I'm not using Ansible myself, but I do use kreadconfig and kwriteconfig, and well, it does just have 4 parameters to identify a setting and its value, so that Ansible module does look like it's sufficient for that.

One tip I have, is that you can figure out which GUI setting corresponds to which config file change, by setting up a Git repo in ~/.config and looking at the diff. So, basically:

cd ~/.config
git init
git add .
git commit -m "original config"
# now change setting in UI
git diff

When you're done transferring that into Ansible, you can commit or stage the changes and tweak another UI setting, or if you're completely done, then just rm ~/.config/.git/.
I guess, you could also use this Git repo to roll back all the settings and see if your Ansible automation works as expected.

Kubuntu still uses Plasma 5.27 which has a lot of issues.

Plasma 6 was rock stable, now 6.1 needs some fixing. I wonder when a more stable version comes.