Once there is support for pre-installed Flatpak apps, all default browsers will be removed
from the base image and the default Flatpak'ed browser won't matter that much
because you will be able to remove it easily. So I did not really spend so much time
thinking about it.
I have plans to add variants for LXQt, Mate, Cinnamon and LXDE but have not found the time
to do it yet. Variants are much easier to create now that the main changes have been
merged in master for 29.
I had a quick a look at Konnolo but I can't include packages from a Copr in the
official KDE release, so I'm afraid this won't go far.