Should work out of the box with Plasma 5/6 (6 if you want HDR) and Sway.
VRR didn’t work with older firmware versions but there have been updates since so the manufacturer information may be out of date. If it doesn’t work, there are links in the gitlab thread for newer firmware (you’ll probably need Windows to update although I saw some vague references that it might be possible on Linux). The adapter is mostly useless on Windows for the record, although you can just swap to a direct HDMI connection in that case.
Oh and I’ll add there are some instances where you may need to power cycle your TV/monitor and/or switch console VTs, if you get a black screen or if HDR fails to toggle on/off.
And lastly, gamescope session didn’t work reliably last time I checked, but it’s been a while.