The last couple weeks have shown steady progress. I got stlink to recognize the chip ID and start flashing, but for some reason it's failing on the last block. I'm not sure what to do about this, other than read app notes and hope to come across a clue or two. ST publishes example code to flash, I might try to get that working before going any further. It may also be a compiling issue, where I need to do something differently when building µpython.
Mad props to the community in the Boldport Slack instance; I wouldn't have gotten this far without their help.