The only immutable distro I’ve tried is Bazzite. It’s gaming-oriented, but can work well as a desktop. It also does offer a KDE edition, but for some reason they intentionally ship with some GNOME programs instead of the KDE ones. For example, a fresh KDE edition installation includes Ptyxis instead of Konsole.
Also, DistroWatch’s search has the option to only show immutable distros. It’s under the Distribution Category option. I figure that might help you find a few more options.
I really just use a power strip and put some tags on my cables so I know what they go to. I keep a few consoles that get a lot of use plugged in at all times. If there’s a brick I only plug them in as needed.
I might look in to getting a RetroTap somewhere down the line.