This was one of the reasons, why I went with one of the Boox devices (Max Lumi) in my case. It is Android, so adding even easier than working around their Linux distro.

Screen sharing (actually it doubles as a remote control as well) via https://github.com/Genymobile/scrcpy

And as they don't try to leverage proprietary formats, Syncthing for syncing books and notes. And NetGuard for a good measure, so it doesn't call home.