We are currently using the automatically generated source tarballs/archives by the git-archive command. In the past those have caused issues due to changes in the git-archive command which changed the checksum of the generated tarballs and therefore broke several packaging workflows relying on git-archive generated tarballs.

An option would be to create an additional workflow to upload source tarballs in the release CI together with a checksum. What would be the best format here? Is everybody fine with tar.xz or tar.zst or should we use zip?

Some package ecosystems have this as soft requirement (I was recently asked to add source tarballs to my releases to contribute a package to spack).