Thanks for the follow-up. Yep— tried Apple Support on the second day when I realised I wasn’t going to rescue the situation either through my know-how or some act of random magic! Support chat had me explain the situation at length, then said I’d need to take it in. Problem was, there were no appointments available, and soon after, the battery died. Half hoping I’ll be able to take it somewhere when the pandemic lifts and someone’ll be able to figure something out, but I’m making peace with the reality that it’s probably just an expensive paperweight now.