SUMMARY Two monitors Systemsettings -> Display and Monitor -> Display Configuration Enable [x] Primary for the monitor currently not, and the full desktop configurations of the two monitors (background image, panel) switch places. Left monitor now has the configuration of the right one and vice versa. Switching primary should not affect the layout of desktops. After all, their position to each other did not change at all. SOFTWARE/OS VERSIONS Operating System: Debian GNU/Linux KDE Plasma Version: 5.23.0 KDE Frameworks Version: 5.86.0 Qt Version: 5.15.2 Kernel Version: 5.14.0-3-amd64 (64-bit) Graphics Platform: X11 Processors: 8 × Intel® Core™ i7-4700MQ CPU @ 2.40GHz Memory: 15,4 GiB of RAM Graphics Processor: Mesa DRI Intel® HD Graphics 4600
This is what the primary monitor setting is expected to do, in fact. We could communicate this better in the UI, but what you are describing is the system working as intended. :)
Hasn't been the case earlier. What exactly has the Primary monitor to do with the position of the desktops? The last time I encountered that setting it was more or less about on what monitor the login (and logout/lock/hibernate/shutdown IIRC) controls appeared. What is the pupose of switching Desktops moving the screens in systemsettings could not achieve?
It's all super buggy, unfortunately. But it sounds like it just started working for you. :) On X11, the current intention is that the Primary Monitor setting determines which screen first "containment" goes. That would be the containment you with your desktop icons, panel, and so on.