The terms of use appear that they handle your data. If you wamt to avoid a thirdparty. i would suggest KDE connect, can combine with tailscale for cross network sends. Syncthing is also good. or Croc for single transfers either local or across networks.
I had a script in termux that used exiftool to rename and organize photos and then rsync them to my backup. That was on an older phone. I need to do that again!
I use KDE connect for that, it works pretty well. I don't use KDE so I'm probably missing out on some features but file transfer, sending clipboard contents, media control etc all work