Error description:
bash: rsync: command not found
rsync: connection unexpectedly closed (0 bytes received so far) [sender]
rsync error: error in rsync protocol data stream (code 12) at /AppleInternal/Library/BuildRoots/b6051351-c030-11ec-96e9-3e7866fcf3a1/Library/Caches/com.apple.xbs/Sources/rsync/rsync/io.c(453) [sender=2.6.9]
Possible solutions:
Verify if rsync is installed on both ends, source and destination. If not install where needed.
Verify if rsync versions are compatible on source and destination
rsync --version