Heroic Launcher requires dropping down to desktop mode once to install the app. Once installed properly it appears as an app inside Steam, which you can launch and then install and play your GOG and Epic games.

I hardly ever do that, but the one time I did (for Minecraft) I did just drop down to desktop mode and used the trackpad and touch screen. This wasn’t really to do with Linux though. Minecraft does not provide any way to install and log in with controller support.

After I installed it one time, I added it to Steam and could launch and update it with a controller. In theory GOG could integrate with Bazzite to offer a controller friendly store and UI. But considering they haven’t even bothered with a desktop Linux client, I’m not holding my breath.