And it's not even Xorg session, it is under Wayland -- Wayland won't allow to set a display mode to apps, and for Xrandr it is faked using overlays with correct density.
> I guess your videocard does not support Vulkan.
Open game properties, Betas tab, switch to "legacy" version. Beware, it will download several gigabytes from internet. Legacy version has support of OpenGL unlinke modern one, which uses only Vulkan.
I actually run Steam inside flatpak - I installed Steam from flathub, launched it, downloaded the games and almost (see below) everything worked. Flatpak runtime has all the necessary Mesa drivers (for AMD and Intel, not sure how Nvidia and flatpak works). The only thing I had to configure myself in the host system was udev rules for Dualshock gamepad. That one breaks the otherwise nice experience of everything working out of the box.
And wrt the Vulkan requirement: that's why I bought The Talos Principle originally. It was one of the first games with Vulkan renderer and I was curious, how well it works.
Ah, I remember trying the Flatpak version of steam but the performance difference was huge (Dead Cells and the dishwasher - vampire smile) with the Steam version of the official site but it was two years ago with an HD4000. Now that you mention it I also remember not wanting to deal with DS controller setup (for games that need it).
I'd have to do some testing with Talos (vs windows version) but I think that The Cave runs smoother now.
On this end, it looks this way, when windowed: https://imgur.com/hlrBFc9
And it's not even Xorg session, it is under Wayland -- Wayland won't allow to set a display mode to apps, and for Xrandr it is faked using overlays with correct density.