I would recommend reaching out to the maintainers of the Fedora package using the (obfuscated) e-mail address listed on the Fedora packages page you linked.
If the Fedora package has been retired, then there are no maintainers to reach by email. You can always check on the status of a Fedora package by visiting https://src.fedoraproject.org/rpms/[package name], which would be Overview - rpms/biboumi - src.fedoraproject.org in this case. That page shows “Retired: Long term failure to build”. If the new repository has fixed the build problems, then somebody could bring the package back. If you would like to do yourself, see Joining the Package Maintainers.
Yes I am sure, because these are well known XMPP developers and the switch was discussed in the official Biboumi xmpp channel that was always hosted by the same team.
The original main developer has a severe case of burnout which is why the others stepped in and moved the repo from the original self-hosted Gitlab instance to Codeberg (the Github one linked above was always just a mirror).