It’s using an x86 compatibility layer, pex i think it was called. So apparently you will be running windows x86 games on it.

Edit: fex! https://github.com/FEX-Emu/FEX

Edit 2, from tom’s hardware article:

The company also showed off the x86 version of Hades 2 running standalone (as in not streaming from a PC) on the Steam Frame. And the game ran just fine and looked good at what Valve reps told me was 1400p in a window inside the headset