If you can selfhost, you can try my SyncMarks AddOn. It will work on any webextension compatible browser, e.g Firefox, Chrome, Chromium, Edge, Brave, Kiwi and so on. You can sync across all Browsers.

The backend is working with selfhosted PHP/MySQL (or SQLITE) stack. If you can’t use this, you can fallback to WebDAV as backend, but with limited functionality.

The addon can work together with the standard sync mechanisms in all these browsers, but it’s up to you if you want that.

If the addon is not installed, you can access the backend url with any browser and use it as WebApp. With apps like Tasker or HTTPShortcuts, you can share any url, from any to the backend.

Maybe… If I use the stable version, it works also sometimes with PROTON_USE_WINED3D=1, but has only 2fps. I can remove this parameter with the dev version and have 45fps.