Syncthing seems to be one of the most used apps when using FreedomBox. I’m using it myself on my FreedomBox, running on a Raspberry Pi 3 B+.
That pre-packaged version is becoming outdated as Syncthing is actively being maintained/developed. The following link contains instructions how to update Syncthing, as recommended by the maintainers.
The repository (currently) contains builds for amd64, arm64, armel, armhf and i386 architectures. Updating requires access via a terminal, which is conveniently available via the Cockpit.
In my case it was a very smooth update. Your mileage may…