I have a very similar setup, but rather than mirroring I have KDE shortcuts that invoke 2 very basic scripts that swap between desktop and livingroom display layouts using kscreen-doctor. It also swaps audio output between HDMI and my audio interface.

Works very well, much better than a similar setup I had on Windows with DisplayFusion. The only thing I have to do is hit the shortcut when sitting down at the desk or the sofa, everything else just works.

Doesn’t this require you to also be on plasma 6.4?

Using proton wayland also breaks steam input, which can be deal breaker.

Getting it to actually work with games is still a crapshoot, though.

Plasma 6.5 has broken tonemapping both with gamescope and proton wayland (which breaks a bunch of other things to boot). The fix was merged just a couple of weeks ago.

Actually very true.