There Perfect Server tutorial for DEBIN Versions up to Buster 10 and there is a fine tutorial for updateing existing Debian 10 servers with ISPConfig to Debian 11. But what about a tutorial installing ISPConfig on a new installed Debian 11 server. Regards Rainer
See here for instructions on installing ISPConfig on Debian 11: https://www.howtoforge.com/ispconfig-autoinstall-debian-ubuntu/