This howto describes how to install a minimal Ubuntu server on a Raspberry Pi 4. Everything is done as the root user in this howto.

Download from: https://ubuntu.com/download/raspberry-pi

Use Etcher or whatever to install the downloaded zip on a SD card.

Default user/pass is ubuntu/ubuntu. It take some minutes to be able to login.

apt update
apt upgrade -y

dpkg-reconfige tzdata

/etc/systemd/timesyncd.conf

[Time]
NTP=172.16.0.254
#RootDistanceMaxSec=5
#PollIntervalMinSec=32
#PollIntervalMaxSec=2048

apt purge cloud-init
rm -rf /etc/cloud
rm -rd /var/lib/cloud
rm /etc/netplan/50-cloud-init.yaml

/etc/netplan/01-netcfg.yaml

network:
  version: 2
  renderer: networkd
  ethernets:
    eth0:
      dhcp4: true

apt purge apparmor

hostnamectl set-hostname raspberry
reboot