I also belatedly realised that Android 12 no longer supports SIP calls natively, so it hasn't been ringing when my home phone does (don't get many landline calls, so hadn't been obvious). Will go with a third-party app instead, although I've previously preferred the native one because I don't trust Android's battery optimisation not to interfere with an always-on app, no matter what I set the battery-saving options to :)