GE-Proton, the unofficial Proton variant by GloriousEggroll, is now also available as a standalone AppImage in version 11-9.

The proton-appimage project by PerseidLab packages GE-Proton releases as self-contained AppImages that run Windows games on Linux with no Steam required. The changes in version 11-9 (including automatic HDR detection) are covered in the article on the actual release.

AppImage build of GE-Proton11-9-x86_64

Source: GitHub