@harryz there are two kinds of SSO (Cloudron user management) setups in Cloudron. One uses LDAP and one uses OpenID Connect. When using LDAP, you will see a normal login form and you can use Cloudron username and password. When using OIDC, you will see a "Login with Cloudron" or "Login with OpenID" button. When you click the button, it will do the SSO dance.
You can differentiate by checking the icon hint on the dashboard. It's on the top left of the grid icon in the apps view (for each app).
The reason for this is some apps support only LDAP. Wherever possible we support OIDC (which we consider more secure).