[Razer Phone 2 Guides, News, & Discussion] LSS4181:
It seems as of Havoc OS 3.2 GSI (Android Q) the ims.apk is not required anymore, and would in turn interfere with the SMS functionality.

After flashing the new GSI I found myself stopped receiving SMS, and tried many different ims.apk files. But turned out wiping every trace of ims.apk from the system instead was what actually fixed it.

From the logcat I discovered this which seemed to indicate that the system was rejecting the ims.apk. And I couldn't find any Google search result regarding the matter.

03-01 21:45:43.695 17907 17926 W Role : org.codeaurora.ims not qualified for android.app.role.HOME due to missing RequiredComponent{mIntentFilterData=IntentFilterData{mAction='android.intent.action.MAIN', mCategories='[android.intent.category.HOME]', mDataScheme='null', mDataType='null'}, mPermission='null', mMetaData=[]}
03-01 21:45:43.701 17907 17924 W Role : org.codeaurora.ims not qualified for android.app.role.DIALER due to missing RequiredComponent{mIntentFilterData=IntentFilterData{mAction='android.intent.action.DIAL', mCategories='[]', mDataScheme='null', mDataType='null'}, mPermission='null', mMetaData=[]}
03-01 21:45:43.704 17907 17926 W Role : org.codeaurora.ims not qualified for android.app.role.EMERGENCY due to missing RequiredComponent{mIntentFilterData=IntentFilterData{mAction='android.telephony.action.EMERGENCY_ASSISTANCE', mCategories='[]', mDataScheme='null', mDataType='null'}, mPermission='null', mMetaData=[]}
03-01 21:45:43.707 17907 17924 W Role : org.codeaurora.ims not qualified for android.app.role.SMS due to missing RequiredComponent{mIntentFilterData=IntentFilterData{mAction='android.provider.Telephony.SMS_DELIVER', mCategories='[]', mDataScheme='null', mDataType='null'}, mPermission='android.permission.BROADCAST_SMS', mMetaData=[]}

EDIT: Sorry, need to test a bit further. Turned out the phone might actually be operating in 3G mode at that time (despite having set LTE as preferred network type). I'm able to actually put it to LTE by setting preferred network time to 3G then back to LTE. Still, removing ims.apk did fix the SMS as I was able to receive all the SMSes I was expecting at that time (but was unable to actually receive), including the older ones. (EDIT 2: The 3G mode issue might be due to poor LTE signal near my workplace so it may not really be the case. Still, the SMS is a hit or miss.)

EDIT 2: Nope it's not quite right (again). The result cannot be trusted as I cannot remember which mode the phone actually was at that time (3G or LTE). However, it seems I'm not able to receive SMS even on 3G mode as well. At that time, in most cases, I can only receive SMS for a brief few seconds when I toggle Airplane mode on then off.

Also, it seems the ims.apk is probably not for Android 10 GSIs. I tried creating an ims.apk from stock MR2 image, based on the build.sh OP mentioned, but the signature's not right and I don't think I have the right environment to generate a platform key signature.

As for the Phone Information (accessed via *#*#4636#*#*), I recall some threads mentioned something about IMS-related stuffs there, but on my GSI (Havoc 3.2) there's no such mention at all.