I would absolutely not want it to work as a controller outside Steam. In initial mode, aka lizard mode, it works as a keyboard and mouse because they want it to be able to boot your OS. That way you can even use it to manage your UEFI settings. Even in bluetooth mode, the og. SC works initially as a mouse. It’s designed for HTPCs after all.

If unsure, go with ext4.

Yes, just deleting Boxtron folder from compatibilitytools.d should do it. You can always play it safe and move it to another location, eg. ~/backup/. Uninstalling dosbox-staging shouldn’t be necessary.

Steam compatibility tools, such as Boxtron, need to install some files in users home directory. These aren’t deleted when software is uninstalled with the package manager. You can check the directory ~/.steam/root/compatibilitytools.d to verify.

There is Plasma Bigscreen that’s a modification for HTPCs. For touch screen based devices, a tiling WM is available for both Gnome and Plasma, though not baked in. IMHO bigger issue for both is a poorly working touch screen keyboard. This is something that SteamOS solves quite well.

My best guess is that you have an GPU that either doesn’t support Vulkan, or has driver issues. But we shouldn’t guess, that’s what logs are for.

For Steam logs, running Steam from terminal as suggested is one way. Do note that error with wrong ELF class for game overlay library when starting any game is normal, since Steam tries to load both 32 and 64 for bit version for each game, and the wrong one will always fail. Arch wiki has more information.

https://wiki.archlinux.org/title/Steam/Troubleshooting#Debugging_Steam

For Proton logs, set environment variable PROTON_LOG=1. You can do it in Steam launch options, see Proton Readme for more info.

https://github.com/ValveSoftware/Proton?tab=readme-ov-file#runtime-config-options

With hardware and firmware issues system logs often point to right direction. Again Arch wiki has a good tutorial on it.

https://wiki.archlinux.org/title/Systemd/Journal#Filtering_output

Games often have their own logging too if you need to go there. You’ll need to look those up, as they vary by game.

I hope this helps.

You could also point Steam custom launch command to PortalWars2Client.exe and leave the files as is, but I suppose you still could be banned.

Proton github has a possible workaround.

https://github.com/ValveSoftware/Proton/issues/8010