Right now we build Kolab 16 for Debian 8/9/10.
Debian 11 (bullseye) is in freeze and should near its release.
So I'd like to suggest to add Debian 11 to Kolab 16 (and winterfell).
Should we drop Debian 8 from Kolab 16?
For Winterfell we should probably drop the old Fedora release.