Update to the update: The creators of the #arch#linux yubikey full disk encryption thing have responded to my bug report with what is essentially a shrug emoji and the line "I hope you had [a backup]".
I don't think that's an appropriate reponse from the maintainers of a critical piece of software like this. I think if you choose to release software like this, you have a responsibility to either make it good or to at the very least warn users that it's bad.
RockyC