pip3 install mpy-utils
It is awfully slow, but seems to work pretty well. Most of the hard work was already done by the excellent fusepy, and thanks to Damien and pyboard.py for the hints on how to get Micropython REPL working in raw mode.
Rather unexpectedly, Tony D from Adafruit made a youtube video about mpy-utils which was quite interesting to see, as it points out quite a few flaws in the package. I’ve tried to turn them into github issues …