Hello, Seems the Package Index for nightly builds are broken for anything below debian bookworm. Last update I got was 5.9.1.20240113-1. There is only a fraction of packages listed in https://packages.sogo.nu/nightly/5/debian/dists/buster/buster/binary-amd64/Packages. Compared to https://packages.sogo.nu/nightly/5/debian/dists/bookworm/bookworm/binary-amd64/ there are no sope and sogo packages listed.
LG Achim Gottinger Systemadministration / Consulting