For the most part, you won’t be able to escape Unix-like paradigms when using Unix-like systems. Notably, users have to exist in some form. You don’t necessarily need to give them passwords for the frontend signage, but they need to exist. The shortlist of setting up cage would be:

• install your favorite server distro of choice
• Have a rootless, sudoless user available to use
• install cage and your app(s) of choice
• Add autologin for the user and edit the user’s BASH profile to autolaunch cage
• Attend to any other backend setup (remote access, only allowing tty1 to exist, etc.)
• reboot

It’s not quite a few clicks, but this can in contrast also be fully automated trivially if it’s something you need to setup more than once.