New Sophos Support Phone Numbers in Effect July 1st, 2023

Migrate RED15 to SD-RED20 connected to Sophos firewall (XG)

We run about seven RED15(w) connected to the Sophos XG. Because of the  the end-of-life (EOL) of the systems we have to replace them with SD-RED20. All systems are productive and we are now looking for an easy way to exchange the systems. The LAN network addresses behind the RED, DHCP and all rules remain unchanged.
How do we approach such an exchange? Is there a related KB article? I still find the RED's switch from UTM to XG.

Added tags
[edited by: Raphael Alganes at 1:09 PM (GMT -7) on 16 May 2023]