Alas, with control to mess something up, I inevitably did (almost certainly an app permission). I was using Google Messages with Chat/RCS turned on, made some permission changes (I think to the sandboxed google play stuff) and was booted from the Chat feature with an endless "trying to verify phone number" message.
I've tried various "fixes" posted online without success, and I'm certain that I noticed it within a day of removing a bunch of permissions (sensors, location, who know what else...) dummy me didn't keep track or know enough to understand the consequences. Just trying to undo my mistake, I'm sure the info is listed somewhere but I'm 100% failing to find it.
Help?