Focusing on a server, the requirements are a bit different. It doesn't matter if the server is physical or virtual. Ubuntu even makes a server distribution tailored to Raspberry Pi's, so this is a good place to start for those.
After installing Ubuntu Server, log in to the machine's console.
Best to enable SSH service so you can connect remotely. This is a nice, up-to-date write up of the different considerations for ssh configuration.
sudo apt-get install openssh-server
Then, SSH access should be on and available remotely
It might be a better idea to use SSH Keys and disable password authentication, especially on a publicly visible server
sudo vi /etc/ssh/sshd_config
From here, it probably makes sense to use configuration management. Documentation is okay too!
If you want a desktop GUI, you can add one:
sudo apt-get install ubuntu-desktop
(This worked for me with a Raspberry Pi 4 with 4GB of memory and Ubuntu Server 20.04)