I bought the Serpente R2 board, and even got uLisp working on it, but can't find any libraries for interacting with its flash chip like it's an SD card. CircuitPython seems able to do it, but I can only find a library allowing sequential access.
Micropython has a lot of files related to this:
Anything vfs seems involved. I suppose, if they're doing it 'manually' that I'm not going to find any pre-written libraries for it... I wish I had the time/ability to extract the work they've done into a library
Turns out I wasn't looking hard enough!
Unfortunately I'm unable to configure that Adafruit library for this board. This is as close as I've got.