Packaging for proj-data is available: https://salsa.debian.org/debian-gis-team/proj-data
It's not in the archive due to license issues with the BeTA2007 grid: https://alioth-lists.debian.net/pipermail/pkg-grass-devel/2020-April/084077.html The issues raised by the FTP masters have been forwarded upstream: https://github.com/OSGeo/PROJ/pull/383#issuecomment-622246695This issue should really be fixed upstream, and not worked around by excluding the problematic grid in a repacked tarball.
