I use Firefox (LibreWolf with Mozilla sync) on multiple devices. To have my tabs, extensions and history easy available I use Mozilla for syncing that data.
Would it be possible to just use a generic sync service like rsync or something, to sync the profile folders and every file in it?
Or would that break or corrupt data?
XBrowserSync and Floccus don’t sync to local files, unless you self-host the server or a webDAV respectively.
Lofloccus makes it easy to spawn a local webDAV server (making Floccus save your bookmarks to local files) which I can then sync with rsync or Syncthing or whatever system I already like. It’s only available for Windows and MacOS though.
Also can easily run a local webdav server with SFTPGo on Linux/BSD/OSX/Windows: https://docs.sftpgo.com/latest/installation/
Or use it directly with your devices to sync instead of going through syncthing.