My starter repo is now uploaded to Github.
The magic that I spent most of my time on fiddling with is in the require replacement:
https://github.com/therabidbanana/playdate-fennel-starter/blob/main/source/main....
I also set was able to figure out how to handle the import statements Playdate lua used via a macro for pd/import from this comment:
https://github.com/bakpakin/Fennel/issues/421#issuecomment-1103070078