SUMMARY
On Wayland I'm experiencing issues with the quick display switcher thingy that pops up with Meta+P, as well as its system tray applet counterpart. If you have a laptop and an external display I encourage you to try switching between all the options for a minute (on Wayland), you are guaranteed to run into various bugs.

Among the issues I personally found are:
- If you first set only the internal display to be active and then switch to only the external display or vice versa, nothing happens. You have to choose "extend to the left/right" first and then choose to switch to the external (/internal) display only in order for it to work
- Sometimes when switching to the internal display, the wallpaper is cut off (likely because the external screen has a different aspect ratio)
- Sometimes when switching around, one of the monitors will have a black background (no wallpaper)
- When choosing any option at all from the quick display switcher, there seems to be a ~25% chance that it will freeze the session completely except for the mouse cursor, and you can't do anything but restart the PC or switch to a TTY

SOFTWARE/OS VERSIONS
Operating System: KDE Neon Unstable Edition
KDE Plasma Version: 5.23.80
KDE Frameworks Version: 5.88
Qt Version: 5.15.3
Graphics Platform: Wayland