all good things

We will do the installation from Ubuntu's mini.iso. The installer is pretty straightforward and similar to the installer of Debian.

1. Grab the mini installation CD from https://wiki.ubuntuusers.de/Downloads/Netzwerkinstallation/#Mini-CD-Image
2. Boot from CD, choose “Install”
3. Selecct your language, country, locale
4. Detect keyboard layout
5. Enter a hostname
6. choose a mirror country
7. create a user
8. confirm the time zone
9. When partitioning disk choose “Guided – use entire disk” and confirm
10. The installer will now install the base system.
11. choose “No automatic updates”
12. In Software selection select nothing, continue
13. Install grub to the MBR
14. choose the appropriate time setting and reboot

After your new installation comes up login as user

• Optional: sudo apt install openssh-server, ssh into your box
• sudo apt install ifupdown
• Edit /etc/network/interfaces

auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug enp0s3
iface enp0s3 inet static
        address 10.0.2.16/24
        gateway 10.0.2.2
        # dns-* options are implemented by the resolvconf package, if installed
        dns-nameservers 1.1.1.1

replace the interface name , address, gateway with your values

Now clean up some unnecessary stuff

sudo systemctl mask systemd-networkd
sudo  systemctl mask systemd-networkd-wait-onlin
sudo  systemctl disable systemd-resolved
sudo  systemctl disable networkd-dispatcher
sudo  systemctl disable systemd-timesncd
sudo  apt remove accountsservice
sudo rm /etc/resolv.conf 

Now edit /etc/resolv.conf

nameserver 1.1.1.1

That's it. Your Ubuntu system runs now with the smallest but still reasonable config possible. On my system it uses 2.0 GB hard disk space and uses 68 MB RAM. Of course, if you now start to install software it is very likely that some of the packages we removed will be pulled in back.

It is also possible to disable systemd-journald with sudo systemctl mask systemd-journald, saving additional RAM, but it will lead to several FAILED messages at boot. But your system will still be functional-

Minimal installation of Xorg with Fluxbox

sudo apt install fluxbox
sudo apt install xinit
sudo apt install xterm

As a user edit ~/.xinitrc exec startfluxbox

Save the file and then type startx. The fluxbox window manager will appear, you should be able to right-click and launch xterm by Applications –> Shells –> Bash