Below is created by VCHA configuration and is sometimes set to DHCP when VCHA is broken.
cat /etc/systemd/network/99-dhcp-en.network
[Match]
Name=e*
[Network]
DHCP=yes
[DHCP]
UseDNS=false
and
10-eth0.network
[Match]
Name=eth0
[Network]
Gateway=172.30.1.101
Address=172.30.1.28/16
DHCP=no
Domains=abc.de
[DHCP]
UseDNS=false
The file can be removed safely and restart the appliance before re-configuring VCHA.