I finished reworking the library to implement the draft bip https://github.com/achow101/bips/blob/musig2-psbt/bip-musig2-psbt.mediawiki and squashed everything into a new initial commit on the master branch. I'll keep the wip branch around for a while so people can see the prior mess (In general I prefer to keep history, but this history is just too messy), if they want to for some reason.
https://github.com/Ademan/rust-musig-psbt/tree/master
Oh and the test transaction I signed https://mempool.space/signet/tx/4598fef988fb1617e4f127c5ff7f115a95587cd86136c354296ce3b8acbf8e0f
I have some tests to fix this week, and many tests to add, and then I'll probably release a 0.1.0 "do not use!" edition.