[Samsung Galaxy Note 8 Questions and Answers] Kalm_Traveler:
thanks! I am looking into this now. As far as I can tell, when the device boots up it is loading some stuff from a recovery partition that overwrites changes made to those root folders/files. I made some changes in init.rc and the file was reverted back when I rebooted.

I know I'm getting really close to completing this, but it's a bit confusing at the moment since I went through file by file and there's just not much left that is different, outside of some of the system apps and libraries, and looking at them comparing the F vs N versions the differences are almost entirely just build specific (like 99% of the file is identical but a short string at the beginning of the file is different - to match the device it was compiled for as far as I can tell).

The libsec-ril files are completely different but those definitely are not part of the equation because Wifi Calling does work with the single-SIM 950N file, and the logcat doesn't have any errors with the RIL.

If I am understanding it correctly now, I see a few issues present on an N950N base with the added F binaries, libraries, permissions, and 950U T-Mobile CSC stuff:

W SchedPolicy: add_tid_to_cgroup failed to write '4433' (Permission denied); fd=47

W ActivityManager: Failed setting process group of 4433 to 1

W System.err: java.lang.IllegalArgumentException: Invalid argument: 4433

W SchedPolicy: add_tid_to_cgroup failed to write '13041' (Permission denied); fd=47

W SchedPolicy: add_tid_to_cgroup failed to write '13173' (Permission denied); fd=48

E NEDI:RECEIVER_CONN: Received Intent of STATE_CHANGE

W ContextImpl: Calling a method in the system process without a qualified user: android.app.ContextImpl.startService:1403 android.content.ContextWrapper.startService:673 com.samsung.tmowfc.wfccontroller.WfcService.updateSignalStrength:170 com.samsung.tmowfc.wfccontroller.WfcPhoneStateListener.onSignalStrengthsChanged:218 android.telephony.PhoneStateListener$1.handleMessage:323

E WifiStateMachine: Did not find remoteAddress {192.168.1.1} in /proc/net/arp

E wlandutservice: Got defaultServiceManager

E [IMS6.0]: ImsEventLoop: select (1), errno (11)

E [IMS6.0]: IMS_onResponse() Resp Id:600

V NativeCrypto: Read error: ssl=0x7ca07d9580: I/O error during system call, Software caused connection abort

V NativeCrypto: SSL shutdown failed: ssl=0x7ca07d9580: I/O error during system call, Broken pipe

W CarrierServices: [1] zzbgb$zza.C: Carrier Services Apk was not found.

W ContextImpl: Calling a method in the system process without a qualified user: android.app.ContextImpl.startService:1403 android.content.ContextWrapper.startService:673 com.samsung.tmowfc.wfccontroller.WfcService.updateRadioState:195 com.samsung.tmowfc.wfccontroller.WfcConnectivityReceiver.parseMobileConnectivity:354 com.samsung.tmowfc.wfccontroller.WfcConnectivityReceiver.processConnectivity:391

W CarrierServices: [1] zzbgb$zza.a: CarrierServices.apk was not found, not pre-loaded or is disabled.

E clatd : Unable to find an IPv6 address on interface rmnet2

E ImsAdaptorImpl: setSSACInfo : ImsAdaptorImpl.

V KeyguardUpdateMonitor: action android.intent.action.SERVICE_STATE serviceState=0 0 voice home data home LTE IWLAN CSS not supported -1 -1 RoamInd=-1 DefRoamInd=-1 VoiceRegType=0 ImsVoiceAvail=1 IsEbSupport=1 IsEaBarred=0 Snap=0 MobileVoice=0 LTE MobileData=0 home LTE PsOnly=false FemtocellInd=0 EmergOnly=false IsDataRoamingFromRegistration=false IsUsingCarrierAggregation=false subId=1

I'm pretty sure the issue is within these logcat lines, but I am having trouble figuring them out.