https://github.com/elvissteinjr/DesktopPlus
Found an actual free open source steamvr desktop overlay. It's better than the default steamvr desktop window, since you can actually move the windows around and attach them to your controller and stuff. And the keyboard has working modifier keys.

It worse than XSOverlay or OVRToolkit, which both have a nice wrist display with clock and battery and can drag around multiple floating windows, while desktopPlus can only do one. But hey, it's free.