Oh dear, OK. This was a fresh install.
I did get the DHCP client working via manual configuration only.
For completeness: The device has two NIC:s, one I225 which NetworkManager called “Wired connection 1”, and the onboard R8125 NetworkManager called “Wired connection 2”. I guess that not should matter though.
(I had a total failure with extending the NetworkManager configuration from only DHCP client on 1 interface only, to do that + do fixed IP on another interface too. NetworkManager bugs, kernel bugs or other bugs crushed the networking on the machine so nothing worked - asked you about this in a separate thread: A horrible failure report in latest Radxa Debian - no networking due to kernel, NetworkManager or other component broken. ifupdown a fix? )