com.heroicgameslauncher.hgl VS com.valvesoftware.Steam.Utility.gamescope

The link you put states that the command is heroic but that would be true only in the first two cases (RPM package from the repos or manually installed). If you installed it as a flatpak from FlatHub, e.g., the command would rather be:

The epic games launcher doesn't have linux support. Download the Heroic Games Launcher from flatpak https://flathub.org/apps/details/com.heroicgameslauncher.hgl

Thanks to the 2.5.0 release of Heroic available on Github (also available as an appimage) and Flatpak now the user has the ability to add Windows executables and installers in Heroic, and preview them in his library, here a little more information about this:

Try Heroic Games launcher, it replaces EGS and GOG launchers.

Install Heroic Games Launcher from the Discover store, it definitely seems like the best way to run Epic and GOG games: https://flathub.org/apps/details/com.heroicgameslauncher.hgl Heroic can then add shortcuts to the games you install to Steam, so you can launch them in game mode.

You could ask the maintainers of the Heroic flatpak to add gamescope as an extension, it should be fairly simple to implement and PolyMC and WarThunder are currently doing that.

You can download Heroic Games from Discover (shopping bag icon) in desktop mode (link to the flathub page: https://flathub.org/apps/details/com.heroicgameslauncher.hgl).

Not really, I just installed the Flatpak from here: https://flathub.org/apps/details/com.heroicgameslauncher.hgl

There is a Flatpak for Gamescope, but it is currently packaged as an extension to Steam's Flatpak, which means that it can't be used outside of that package. Someone opened an issue because it has been recognized that this is a problem for other launchers. Someone has written a manifest to build a Flatpak that exposes it as a Vulkan layer, but it's kind of a big hack and you're not likely to see it in Flathub as it currently is. Running any application with it is very clunky. The author of that manifest feels that Gamescope should be added to the FD.O runtime, but that's not particularly likely. Still, follow that linked issue report for developments on this.

There is a gamescope flatpak. I've never tried using it though.

Please carefully test everything you can. I only tested Gamescope and that part seems to work well. If you want to test out Gamescope, please install com.valvesoftware.Steam.Utility.gamescope: flatpak install com.valvesoftware.Steam.Utility.gamescope.

Flatpak version: https://github.com/flathub/com.valvesoftware.Steam.Utility.gamescope