Disabling encryption for internal network

[Dark Empathy]

Hi,

Please excuse the simple question, but I am unable to work out what to do
from the man page alone.

What is a way to disable encryption for an internal network, where it is
not required? (Linux to Linux).  Is this possible with perhaps a rsync
server and --remote-schema?

I have a situation where we have data on Raspberry Pi 3's. spread over a
private WAN.  Data security, in this particular case, is of zero
importance.  However, I would prefer not to disable encryption on the SSH
server.

Are there any suggestions to run rdiff-backup at maximum speed, no
encryption, on an internal network?

Thankyou kindly.