There are no instructions for configuring gitea when installed from snap

Configuration instructions for gitea install from snap store are required.

sudo snap install gitea really doesn’t seem adequate - given my experience with the result.

ubuntu@gitea:~$ sudo snap install gitea 
ubuntu@gitea:~$ sudo systemctl status gitea
Unit gitea.service could not be found.
ubuntu@gitea:~$ sudo systemctl daemon-reload
ubuntu@gitea:~$ sudo systemctl enable --now gitea
Failed to enable unit: Unit file gitea.service does not exist.

I can run gitea from the command line.
Instructions to configure as a service are required I think.

It is there - as easy as can be. Just install snapd, then install the snap.

$ systemctl status snap.gitea.web.service
● snap.gitea.web.service - Service for snap application gitea.web
     Loaded: loaded (/etc/systemd/system/snap.gitea.web.service; enabled; vendor preset: enabled)
     Active: active (running) since Mon 2022-09-05 15:27:48 AEST; 16min ago
   Main PID: 208 (gitea)
      Tasks: 14 (limit: 18728)
     Memory: 188.8M
        CPU: 1.550s
     CGroup: /system.slice/snap.gitea.web.service
             └─208 /snap/gitea/6068/gitea web

Can you configure a database or is one provided in the snap?

You can use Gitea with SQLite by default with the snap without installing other packages. Any other databases you will have to install and configure additional packages. If this is going to be large installation or performance is wanted, it is better to use alternate database like PostgreSQL or MariaDB.