OK… I was able to restart the net settings and it connected & finished the DietPi update as well as the Raspberry Pi software.
root@JacoPi:~# cat /etc/resolv.conf
# Generated by dhcpcd from eth0.dhcp
# /etc/resolv.conf.head can replace this line
nameserver 1.1.1.1
nameserver 1.0.0.1
# /etc/resolv.conf.tail can replace this line
Now for reasons unknown it’s offline again. But now this seems to be a RaspberryPi software issue rather than a DietPi OS thing.