[OnePlus 7T Pro 5G McLaren Questions & Answers] siani_8:
So here I am back on 10.0.36 again. Initial boot offline produced sounds again for about 2 minutes before they disappeared again.

Resetting system settings was a no go so I started with usual and uninstalled any apps that it would allow me to uninstall through settings.

To sum up all of the small changes and many reboots, I disabled all of the unhidden/non-system Google apps except for Play Services and GBoard but I did swap that out for Simple Keyboard (installed from internal storage). Before disabling them I revoked their rights to modify system settings as well as display over other apps.

I left T-Mobile enabled but denied it's rights to modify system apps.

I took all of the background data permissions away (probably isn't related to the sound issue but just didn't thing disabled apps should have that option checked anyway) from the Google apps. After rebooting most of those like Duo, Calender, Pay, Maps, etc but not the Google App itself all had the permissions for background data again, presumably because I did not deny Google Play Services access to change system settings. I can't be sure it was play services doing that though because I didn't turn that permission off for all apps (mostly system).

Android Auto is disabled. I denied Mic for the T-Mobile app. There's a couple other ones I disallowed to display over other apps and modify system settings and I also cleared cache for all of the apps I made changes to.

Sounds (system, ringtones, etc. are now holding fine and it's been over an hour. Mic was confirmed by installing a recorder app from storage.

I'm not sure about anything but this once again seems to suggest that my hardware (at least the actual speakers and mic) is fine and that maybe if I get on a custom rom with minimal Google interference, I have a shot at using this darn thing. Haven't read that section as extensively as the rest of the sections though because better understanding of stock is always better before jumping into the experimental. I do hope there's one I can use that doesn't bring my apparent conflict with the Google with it.

In the meantime, I guess I need to worry about a reboot that initiates Android 11 (if I take it off airplane mode) because to date, I haven't figured out what, if any changes, I can do in settings to get my sound and mic back if it updates to the newest OTA flavor.

I took one suggestion so far I saw in the thread about creating a payload_metadata.bin with no permissions....sounds plausible. There was an alternative suggestion through magisk but I'd have to open the internet flood gate again for that. So far I only let internet down long enough to let magisk install with the latest update because installing it as a zip through a booted TWRP (latest) doesn't install it fully until I let it have internet access and I left it open long enough to get a couple modules, one being the one that allows the editing of build props in case there's a suggested change I see that can be made to audio that is causing my conflict. That of course was long enough for the system to at least download Android 11 somewhere on my device.

I'm really not sure if there's a hardware difference with my device or something with the Persist (just a guess) that comes back no matter what fresh start with whatever stock RoM I choose to use with the Unbrick Tool but there's obviously something different about this device or I wouldn't be seemingly the only one with this issue.

I guess at this point I'll search for the best way to stop the OTA from installing and look into the best custom RoM option for myself because as tenacious as I am, I just don't have the luxury of the time it would take for the deeper understanding necessary to do this alone. I've done so much reading just for the reward of having a phone that can at least make a phone call lol.

Edit: Oh yeah XGoogle enrollment is disabled too.

EDIT: IF I REMOVE "ALLOW TO MODIFY SYSTEM SETTINGS" PERMISSION FROM TOO MANY OF THE GOOGLE APPS, NOT INCLUDING PLAY SERVICES, MY DEVICE WILL FACTORY RESET ITSELF. USING THE PHONE WITH SIM AND WIFI BUT WITHOUT EVER SIGNING INTO ANY GOOGLE SERVICES CAUSES A FACTORY RESET ALSO. THIS IS USUALLY INITIATED BY LETTING THE PHONE SIT IDLE FOR TOO LONG BUT MAKING A PHONE CALL SEEMS TO MAKE IT CRASH AROUND 5 MINUES FROM CONNECTION TO THE CALL.