Depends on #1674

This already includes #1679

Can we add Unreal icon fix in this PR too?

NOTE:
We could maybe move the project preparation from prelaunch hook move to Python script which is executed as different process. So it's separated from tray and we may be able to display that "something is happening" with progress bar?

Tried only on Windows (it's not only linux changing) and it works. I have to trust that it works on linux as that needs to be compiled which I'm not capable of. It works from 4.26 on. We should mention that in docs if it's not there.

We should even stop from trying to run it with older versions.

Can we add Unreal icon fix in this PR too?

Damn, I thought it is already in.

We could maybe move the project preparation from prelaunch hook move to Python script which is executed as different process. So it's separated from tray and we may be able to display that "something is happening" with progress bar?

Possibly, but where would you display such progress bar?

Possibly, but where would you display such progress bar?

It is just an idea for future feature. Because if you'll run python script you can use Qt in it (like we do in nonpython hosts). But that may also cause other issues.