I have grown sick of the return of the monitor lottery as I call it. The idea that there is no predictability of where an application will start on what monitor. It has returned with Plasma 6 it was solved in Plasma 5. An application would start on the monitor where the taskbar is and if moved to another monitor in Plasma 5 then shut down it always opened on it when next started. The Plasma 6 good luck with that working properly it is back to the lottery seeing if you win to get the damn thing started where you left it and the best part is I have three monitors one of which is shut off except when I play my video. This is invariably the monitor Plasma 6 will choose to play the lottery with most times. Today I download the Glaxnimate 0.6.0 Beta .AppImage to see what it is all about an the thing starts up with greyed out screen not being able to do anything, after few minutes I finally clue in to turn on the other monitor just before doing logout to see if that kills off what I am thinking is piece of junk app, sure enough there is a opening dialog of it sitting there that when dismissed gives me functioning app. To say I am not impressed with the return of this lottery feature is a mild understatement. x11 is the system in use the majority of the time, the wayland is even worse, with it mostly none of the applications will start on the monitor last started on most times I have ever tried it to test it out, at least with x11 the vast majority will start where they were last opened.
I know this wasn’t posted in the Help category, but for what it’s worth - in general, I believe windows are intended to open on the screen that last had some interaction from the user. If that’s not working, and the symptoms described in 491230 – applications opening on wrong screens / window rules to force screen not working are what you’re experiencing, I would suggest adding yourself to the CC list on that bug so you can be notified more easily of any updates.
Windows did open that way, it was a talking point in one of Nate’s blog entries how it had finally been solved in Plasma 5. And it had for the longest time it just worked, upgrade to Plasma 6 and the regression is there back to the old state of things with them seemingly opening wherever they want to. No need for help that is why I posted in General the problem was already known and solved, the fix was left out of new effort.