To circle back on this, it certainly seems like the Trip computer is a bit messed up. My first trip since last week yielded this nonsense:
View attachment 28124
I reset the Trip A before leaving, so the "Since Last Charge" does show the correct number of miles. However, the kWh and the Mi/kWh are back to funny business. The Trip A and the Trip B (my lifetime numbers) seem to be reasonably correct.
I'll do a software reset before my next charge. Hopefully that'll fix it. Medium term plan is to follow
@borski advice and take a crack at Home Assistant. That'll give me more numbers than I know what to do with