How the heck do I get gamescope working with Heroic Games Launcher?
This is one is very confusing, which probably speaks to the current UI in Heroic. I just want to say, run this game in gamescope, so I can use HDR.
I have the latest version of Heroic, installed via Flatpak as the devs recommend. If I go to configure the game in the UI it has an entire settings page dedicated to Gamescope but nothing that says "enable gamescope".
What GPU you are running? If it's not a recent AMD gpu, that might be the cause. Relatively recent Mesa and kernel would be a good idea too. The flatpak situation could complicate that too, as others have mentioned.
Monitors/displays can sometimes be temperamental too, and require toggling on/off, switching VTs back and forth, etc.
Beyond that, I'd try installing standard Steam if possible.