Can I sync folders in two devices over Bluetooth? Can I sync folders and files in two Android devices? These devices are physically nearby, but not connected to the same Wi-Fi network. They are connected to the internet using their respective mobile data connection.
Maybe there's a possibility using e.g. Bluetooth and maybe use Wi-Fi Direct when large data transfer is needed?
I dont want  AirDrop or NearbyShare like functionality. It is rather like Resillo or Syncthing over bluetooth.
Well I can't really say &quot;sync&quot; but the closest tool you can use is : Bluetooth File Transfer.
Its free (with ads) with option of non ad version at a price, but still good enough for the former option.

It allows you to use your smartphone to browse, explore and manage
files of any Bluetooth ready device, using File Transfer Profile (FTP)
and Object Push Profile (OPP): you can also receive files and send
contacts!

It provides its own OBEX layer, additionally you can cut, copy, move, paste, delete multiple items using the integrated explorer of this application.