Yes that is one of the problem. The doc talks about snap installation or manual installation, but I don’t really see how to access nextcloud in case of snap install. I suppose I have to config apache2 to get access but in case of package install, the config is not clear to me.
You’re mixing two different parts of the docs. The snap install is self-contained-- you don’t need to configure Apache, and in fact you shouldn’t even have apache installed or it will claim port 80 and the snap won’t be able to. Either uninstall Apache or configure Apache or the snap to listen on another port.