Thanks, I am awarw of that, I also have an rsync job to move the files into my NAS. The deletion is the part that bothers me most, but if you flash the device and the install syncthing with a new identifier that should treat it as a new device.

I use Syncthing to back up my Signal chats and pictures every night with my raspberry Pi. I simply let Signal create a backup at night ans let Syncthing watch the backup folder.