Several Plasma components such as KRunner and notifications do not respect the Primary display option and insist on showing up on the monitor plugged into the first displayPort on my GPU (DP-01).
STEPS TO REPRODUCE
1. Get a notification on Plasma or activate KRunner. Likely also affects other Plasma components.
2. Will appear on display that is the display plugged into the first port on your GPU and not the display marked as primary.
Plasma components do not respect primary monitor setting.
Plasma components such as notifications and KRunner should either appear on the primary display. KRunner likely should appear on the display that your cursor is on, but other plasma components do not respect the Primary display setting either when they likely should.
Linux/KDE Plasma: 5.16.0-arch1-1
KDE Plasma Version: 5.23.90
KDE Frameworks Version: 5.90.0
Qt Version: 5.15.2
In my use case, my primary monitor is unfortunately a monitor in the top corner of my setup, meaning it is easy to miss notifications and inconvenient to look up and use KRunner on it every time.
Notification placement has nothing to do with what the primary monitor is. Notifications appear on the screen where the notification applet is placed
I'm not sure I have a specific notification applet apart from the one in the system tray, which I have in each of my 4 panels on each display. Maybe this should be a separate report, I remember seeing discussion before around where notifications should appear and I just assumed from a user perspective that they would appear on the primary display.
Notifications used to appear on my the top middle display, as it was in the DP-02 port. Now that there is a display in the DP-01 port, it seems to be the one that takes priority for notifications and KRunner. I had thought setting the primary display would change this behaviour.
for both krunner personally i would prefer it to appear on the screen with a currently focused window (notifications when there is an applet per display i guess that would also apply, otherwise yeah, whatever the screen with the applet)
krunner at he moment tries to appear in the screen with the cursor in it, but this of cource can only work on x11, so on wayland that's broken, and will always appear on the screen that contains 0,0 in its geometry, so the left-most
For notifications, see Bug 446961.
Let's use this bug report to track the issue with KRunner.
Just for what it's worth with the renaming of this bug: KRunner does *not* always appear on the left-most screen. It always appears on the screen with 0,0 I believe, but that isn't always the left-most. In my case, I have a monitor in the top middle which i will assume is 0,0 however this is the screen that KRunner appears on. So in some setups, the title of this bug is inaccurate.
*** This bug has been marked as a duplicate of bug 427069 ***