We just need to rally together a community that would maintain such a fork.
https://github.com/bitwarden/ios?tab=GPL-3.0-1-ov-file
Is proprietary config required to build the IPA file?
Looking into it again, it seems like the Apple Media Services T&C now has provisions for distributing apps under a "Custom EULA", but it still has weird clauses like the one saying you can't "scrape, copy, or perform measurement, analysis, or monitoring of, any portion of the Content", which their definition of includes apps. (Ridiculous clause since it prohibits so much as looking at an app with Activity Monitor, but whatever.) The GPLv3 has a provision saying users can ignore additional restrictions, but you as an App Store uploader aren't in a position to grant that right, so... the situation still seems legally iffy enough that I'm not sure you could win against Bitwarden if they objected to a fork.