I have two monitors, one 1440x3440 and one 1080x1920 to its right. Every boot, the desktop on my left monitor moves over and displays on top of the right one. Killing and restarting plasmashell moves it to where it should be, but i'd love to fix this without adding that to my .xsession. Thing is, i'm not versed enough in the KDE internals to know where this issue even stems from.
I'm running EndeavourOS with Plasma 6.1.5 on X11. I haven't tried wayland since Plasma 6 switched to it and then promptly flickered itself into a crash.
Edit: This machine runs the amdgpu-pro driver, and has done since before plasma 6 released. i didn't have this problem on plasma 5.
The right monitor is indeed first when enumerating, but it's also an old-ass monitor that runs over DVI while the newer monitor is on HDMI since i can't get it to its correct refresh rate otherwise. no way to swap them around i'm afraid.
I've done the primary switch trick before, and it works, but it's just as temporary as just killing plasmashell, and that's less keystrokes. deleting the cache also works for a boot or two, but as you say it's a bit of a nuclear option.
Honestly, part of the reason i'm asking here is that i can't navigate the kde bugtracker. I've tried looking for issues relating to kwin, plasmashell, desktop, graphical errors, but i either get thousands of vaguely related issues or nothing.