My System Info

Linux Distribution: Ubuntu 20.04 LTS
Desktop Environment: GNOME
Graphics Card: GeForce MX250
GPU Driver Version: 460.39

Have you checked for system updates?: Yes

If this is to do with Steam, please add your system read-out from Steam -> Help -> System Information (please put that into Pastebin/Gist as linked above!):
https://pastebin.com/hcwutp63

You can note your issue below here
Default display for video output when running games via Steam is inconsistent.

Note any particular steps to reproduce it below here
* Connect external display via HDMI, ensure that it is the default display in Ubuntu's settings (Settings-->Screen Display-->Screen Display-->Primary Display-->2 Samsung Electric Company 27")
* Ensure that all other displays are "active" (Settings-->Screen Display-->Screen Display-->)



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I have a dual-display laptop (i.e. my laptop has two built-in displays) and I have an external display connected via HDMI, however my primary display is the external display (both in actual usage, and also in Ubuntu's settings).

But when I run games with Steam, the display on which games appear by default is inconsistent.

Sometimes games will default to the external display, sometimes they will default to my laptop's primary display (they never default to my laptop's secondary display, presumably because it's physically smaller than the other two).

In addition, the display output is often different even between games of the same developer and / or series (e.g. "Portal" defaults to my external display, but "Portal 2" defaults to my laptop's primary display); and one game (Plague Inc: Evolved) - which was previously defaulting to the external display - now defaults to the primary display on my laptop after downloading some downloadable content.

I can force everything onto my external display by disabling the other two displays in Ubuntu's settings - but with three displays, this is a pain to do every time I want to do some gaming...

Surely there's a way to force games to appear on my external display, when using Steam (obviously I still want them to revert to my laptop's primary display, if disconnected from my external screen)?