You can ship DRM-free games on it just fine. It's up to the dev/publisher. Additionally you can get a lot of the benefits of Steam (Proton etc.) even for title

You can ship DRM-free games on it just fine. It's up to the dev/publisher. Additionally you can get a lot of the benefits of Steam (Proton etc.) even for titles you didn't acquire through Steam - you can add and launch third party executables through the Steam client. Steam is not exactly a walled garden save for some rather light curation of their own store.