I’m using Ubuntu Server 20.04.3 LTS on a seperate machine.
The link I typed in is https://(the seperate machines ip):8443 and the link above is what I see after I log in.
Welcome!
I would backtrack and redo the installation as I think you forgot to run a step.
https://minecraft.codeemo.com/mineoswiki/index.php?title=MineOS-node_(apt-get)#:~:text=recent%20enough%20version.-,Installing%20MineOS%20scripts,-git
Are you installing as root?