welcome to the forum,
i would not trust rclone serve to be used for backups.
freebsd and linux, both support the built-in sftp server and samba.
use rclone sync on the source machines.
and make sure to use checksums to verify file transfers.
as a side issue, i have a howto guide about rclone+smb|samba
https://forum.rclone.org/t/how-to-access-smb-samba-with-rclone/42754
@kapitainsky, any suggestions?