Dear Maintainer,
*** Reporter, please consider answering these questions, where appropriate ***
* What led up to the situation?
Fresh install of Debian 11 Live ISO with non-free firmware. Error messages occured aftr fresh install - systemctl status network.service displayed error message that dhclient had issues during start.
I traced the error back to the unit file of systemd network.service - the command "ifup -a --read-environment" lead to the error, because the file /etc/network/interface.d/setup had eth0 as general
network interface.
* What exactly did you do (or not do) that was effective (or
ineffective)?
I replace eth0 in the file /etc/network/interface.d/setup with the correct network interface identifier "enp7...".
* What was the outcome of this action?
This particular error message was gone after the changes that I applied.