Fresh Debian 11 netinstall fails:"apt-get install "task-gnome-desktop" unable to locate package
Okay i got it. The minimal-installer has (for this Case) missing dependencies in /etc/apt/sources.list.
I Had to add:
deb http://deb.debian.org/debian bullseye main deb-src http://deb.debian.org/debian bullseye main
deb http://deb.debian.org/debian bullseye-updates main deb-src http://deb.debian.org/debian bullseye-updates main
I gathered this information here: https://wiki.debian.org/SourcesList
Depending on your system "non-free" and "contribut" (could) must be added as attributes as well.