Hello https://discussions.apple.com/profile/Lawrence+Finch thanks for all your suggestions. I have rechecked them again and here is where we (still) are:
The calls weren’t logged as missed because I grabbed them to answer but only just as the other party was hanging up.
I was unable to return the call because it would have been routed to the request for return call again, although I did do this a few times. So there was no question as to whether these calls were being made or missed. It was only that there was never an audible ring to alert me in time. I saw with my eyes that a call was being attempted when I picked up my silent phone and noticed it only to not be able to react in time.
I did later check for carrier outages and none were listed for the time frame, though that kind of test made no direct sense because I could see the calls on my screen. But I checked anyway and there were none for that time period.
Focus is disabled.
But: Share Across Devices was enabled. Being useless for myself at this time, I have turned this off.
In Sounds/Haptics, there is a functioning, system sound selected for ringtone.
Auto answer calls is off.
MUTE switch was off, as above.
Volume was up full. Ringer is not impacted by buttons on my phone by choice.
Silence unknown callers is off (thanks for reminding but it was off).
Screentime is off. Out of curiosity, why would I need that on, with communications limits to everyone?
ios 15.3.1:
thx