[OnePlus 8T ROMs, Kernels, Recoveries, & Other Deve] luspi:
It crashes with the default LOS SMS app, but I was able to successfully forward a text message using another SMS app (I think it was Simple SMS, the first one I found in F-Droid).

I haven't been able to convince the default LOS SMS app to do this, restarting, emptying cache and storage, all doesn't seem to help. Not sure what else to try...

Edit: I believe I found the relevant entries in the log file, maybe it helps someone figure out what the cause might be?

01-14 20:51:00.464 23977 23977 E MessagingApp: Expected condition to be true
01-14 20:51:00.465 23977 23977 E MessagingApp: at com.android.messaging.ui.conversationlist.ForwardMessageActivity.onAttachFragment(Unknown Source:2)
01-14 20:51:00.465 23977 23977 D AndroidRuntime: Shutting down VM
01-14 20:51:00.466 23977 23977 E AndroidRuntime: FATAL EXCEPTION: main
01-14 20:51:00.466 23977 23977 E AndroidRuntime: Process: com.android.messaging, PID: 23977
01-14 20:51:00.466 23977 23977 E AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.messaging/com.android.messaging.ui.conversationlist.ForwardMessageActivity}: java.lang.ClassCastException: androidx.lifecycle.I cannot be cast to com.android.messaging.ui.conversationlist.ConversationListFragment
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3645)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3782)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:101)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2307)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:106)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.os.Looper.loopOnce(Looper.java:201)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.os.Looper.loop(Looper.java:288)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:7872)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:936)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: Caused by: java.lang.ClassCastException: androidx.lifecycle.I cannot be cast to com.android.messaging.ui.conversationlist.ConversationListFragment
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at com.android.messaging.ui.conversationlist.ForwardMessageActivity.onAttachFragment(Unknown Source:5)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.Activity$HostCallbacks.onAttachFragment(Activity.java:9008)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1253)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.FragmentManagerImpl.addAddedFragments(FragmentManager.java:2431)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2210)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2166)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2067)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:822)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at androidx.lifecycle.I.b(Unknown Source:31)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at androidx.lifecycle.LifecycleDispatcher$DispatcherActivityCallback.onActivityCreated(Unknown Source:0)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.Application.dispatchActivityCreated(Application.java:368)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.Activity.dispatchActivityCreated(Activity.java:1372)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.Activity.onCreate(Activity.java:1654)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at com.android.messaging.ui.BaseBugleActivity.onCreate(Unknown Source:0)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at com.android.messaging.ui.conversationlist.ForwardMessageActivity.onCreate(Unknown Source:0)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.Activity.performCreate(Activity.java:8305)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.Activity.performCreate(Activity.java:8284)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1417)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3626)
01-14 20:51:00.466 23977 23977 E AndroidRuntime: ... 12 more
01-14 20:51:00.468 1664 372 I DropBoxManagerService: add tag=system_app_crash isTagEnabled=true flags=0x2
01-14 20:51:00.468 1664 7528 W ActivityTaskManager: Force finishing activity com.android.messaging/.ui.conversationlist.ForwardMessageActivity
01-14 20:51:00.475 1664 7528 W ActivityTaskManager: Force finishing activity com.android.messaging/.ui.conversation.ConversationActivity
01-14 20:51:00.478 23977 23977 I Process : Sending signal. PID: 23977 SIG: 9
01-14 20:51:00.492 1664 7528 I WindowManager: WIN DEATH: Window{50124cf u0 com.android.messaging/com.android.messaging.ui.conversation.ConversationActivity}
01-14 20:51:00.493 1664 7528 W InputManager-JNI: Input channel object '50124cf com.android.messaging/com.android.messaging.ui.conversation.ConversationActivity (client)' was disposed without first being removed with the input manager!
01-14 20:51:00.495 1664 13441 I ActivityManager: Process com.android.messaging (pid 23977) has died: fg TOP
01-14 20:51:00.495 1664 1813 I libprocessgroup: Successfully killed process cgroup uid 10128 pid 23977 in 0ms
01-14 20:51:00.495 928 928 I Zygote : Process 23977 exited due to signal 9 (Killed)
01-14 20:51:00.496 1664 13442 I WindowManager: WIN DEATH: Window{d33d555 u0 com.android.messaging/com.android.messaging.ui.conversationlist.ConversationListActivity}
01-14 20:51:00.496 1664 13442 W InputManager-JNI: Input channel object 'd33d555 com.android.messaging/com.android.messaging.ui.conversationlist.ConversationListActivity (client)' was disposed without first being removed with the input manager!
01-14 20:51:00.498 1664 13441 W ActivityManager: Scheduling restart of crashed service com.android.messaging/.datamodel.action.ActionServiceImpl in 1000ms for connection
01-14 20:51:00.504 1664 1806 W UsageStatsService: Unexpected activity event reported! (com.android.messaging/com.android.messaging.ui.conversationlist.ConversationListActivity event : 23 instanceId : 252185735)
01-14 20:51:00.537 2121 2264 E OpenGLRenderer: Unable to match the desired swap behavior.
01-14 20:51:00.538 928 928 D Zygote : Forked child process 376
01-14 20:51:00.538 1664 1808 I ActivityManager: Start proc 376:com.android.messaging/u0a128 for top-activity {com.android.messaging/com.android.messaging.ui.conversationlist.ConversationListActivity}
01-14 20:51:00.539 2121 2264 W Parcel : Expecting binder but got null!
01-14 20:51:00.546 376 376 I libc : SetHeapTaggingLevel: tag level set to 0
01-14 20:51:00.561 376 376 E droid.messaging: Not starting debugger since process cannot load the jdwp agent.
01-14 20:51:00.344 376 376 I (6)[376:droid.messaging]binder: 376:376 ioctl 40046210 7ff8014470 returned -22
01-14 20:51:00.569 1664 1801 W WindowManager: Exception thrown during dispatchAppVisibility Window{50124cf u0 com.android.messaging/com.android.messaging.ui.conversation.ConversationActivity EXITING}
01-14 20:51:00.569 1664 1801 W WindowManager: android.os.DeadObjectException
01-14 20:51:00.569 1664 1801 W WindowManager: at android.os.BinderProxy.transactNative(Native Method)
01-14 20:51:00.569 1664 1801 W WindowManager: at android.os.BinderProxy.transact(BinderProxy.java:584)
01-14 20:51:00.569 1664 1801 W WindowManager: at android.view.IWindow$Stub$Proxy.dispatchAppVisibility(IWindow.java:536)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.WindowState.sendAppVisibilityToClients(WindowState.java:3481)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.WindowContainer.sendAppVisibilityToClients(WindowContainer.java:1228)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.WindowToken.setClientVisible(WindowToken.java:392)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.ActivityRecord.setClientVisible(ActivityRecord.java:6725)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.ActivityRecord.onAnimationFinished(ActivityRecord.java:7537)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.ActivityRecord.postApplyAnimation(ActivityRecord.java:5416)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.ActivityRecord.commitVisibility(ActivityRecord.java:5375)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.ActivityRecord.commitVisibility(ActivityRecord.java:5379)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.AppTransitionController.handleClosingApps(AppTransitionController.java:1147)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.AppTransitionController.handleAppTransitionReady(AppTransitionController.java:292)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.RootWindowContainer.checkAppTransitionReady(RootWindowContainer.java:981)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.RootWindowContainer.performSurfacePlacementNoTrace(RootWindowContainer.java:837)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.RootWindowContainer.performSurfacePlacement(RootWindowContainer.java:779)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.WindowSurfacePlacer.performSurfacePlacementLoop(WindowSurfacePlacer.java:177)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.WindowSurfacePlacer.performSurfacePlacement(WindowSurfacePlacer.java:126)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.WindowSurfacePlacer.performSurfacePlacement(WindowSurfacePlacer.java:115)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.wm.WindowSurfacePlacer$Traverser.run(WindowSurfacePlacer.java:57)
01-14 20:51:00.569 1664 1801 W WindowManager: at android.os.Handler.handleCallback(Handler.java:942)
01-14 20:51:00.569 1664 1801 W WindowManager: at android.os.Handler.dispatchMessage(Handler.java:99)
01-14 20:51:00.569 1664 1801 W WindowManager: at android.os.Looper.loopOnce(Looper.java:201)
01-14 20:51:00.569 1664 1801 W WindowManager: at android.os.Looper.loop(Looper.java:288)
01-14 20:51:00.569 1664 1801 W WindowManager: at android.os.HandlerThread.run(HandlerThread.java:67)
01-14 20:51:00.569 1664 1801 W WindowManager: at com.android.server.ServiceThread.run(ServiceThread.java:44)
01-14 20:51:00.569 1664 1801 I Process : Sending signal. PID: 23977 SIG: 9
01-14 20:51:00.569 376 376 D CompatibilityChangeReporter: Compat change id reported: 171979766; UID 10128; state: DISABLED
01-14 20:51:00.570 1664 1800 W ActivityManager: setHasOverlayUi called on unknown pid: 23977
01-14 20:51:00.571 376 376 D ApplicationLoaders: Returning zygote-cached class loader: /system/framework/android.test.base.jar
01-14 20:51:00.573 1228 1228 E ClientCache: failed to get buffer, invalid process token
01-14 20:51:00.575 1228 1228 E BpTransactionCompletedListener: Failed to transact (-32)
01-14 20:51:00.584 376 376 D nativeloader: classloader namespace configured for unbundled product apk. library_path=/product/app/messaging/lib/arm64:/product/lib64:/system/product/lib64
01-14 20:51:00.591 376 376 V GraphicsEnvironment: ANGLE Developer option for 'com.android.messaging' set to: 'default'
01-14 20:51:00.591 376 376 V GraphicsEnvironment: ANGLE GameManagerService for com.android.messaging: false
01-14 20:51:00.591 376 376 V GraphicsEnvironment: Neither updatable production driver nor prerelease driver is supported.
01-14 20:51:00.593 376 376 D NetworkSecurityConfig: No Network Security Config specified, using platform default
01-14 20:51:00.593 376 376 D NetworkSecurityConfig: No Network Security Config specified, using platform default
01-14 20:51:00.602 376 376 D CompatibilityChangeReporter: Compat change id reported: 194532703; UID 10128; state: DISABLED
01-14 20:51:00.604 376 376 D CompatibilityChangeReporter: Compat change id reported: 160794467; UID 10128; state: DISABLED
01-14 20:51:00.608 1664 13442 D CompatibilityChangeReporter: Compat change id reported: 161145287; UID 10128; state: DISABLED
01-14 20:51:00.611 376 523 W MessagingApp: canonicalizeMccMnc: invalid mccmnc:null ,null
01-14 20:51:00.612 376 523 I MessagingApp: Carrier configs loaded: Bundle[{httpSocketTimeout=60000, aliasMinChars=2, smsToMmsTextThreshold=-1, enableSMSDeliveryReports=true, maxMessageTextSize=-1, supportMmsContentDisposition=true, enabledTransID=false, aliasEnabled=false, supportHttpCharsetHeader=false, allowAttachAudio=true, smsToMmsTextLengthThreshold=-1, recipientLimit=2147483647, uaProfTagName=x-wap-profile, aliasMaxChars=48, maxImageHeight=1944, enableMMSDeliveryReports=false, userAgent=, mmsCloseConnection=true, config_cellBroadcastAppLinks=true, maxSubjectLength=40, httpParams=, enableGroupMms=true, emailGatewayNumber=, maxMessageSize=1048576, naiSuffix=, enableMMSReadReports=false, maxImageWidth=2592, uaProfUrl=, enabledMMS=true, enabledNotifyWapMMSC=false, sendMultipartSmsAsSeparateMessages=false, enableMultipartSMS=true}] from resources+system for subId=1