@joseph Thanks. I've added the code below in Nextcloud's config.php and it works fine.
'social_login_auto_redirect' => true,
'hide_login_form' => true,
Now I just wish to know if there is a way to remove or change the default text on the login window (?)
"The Nextcloud login form is disabled. Use another login option if available or contact your administration."
No big deal if not possible.
Best wishes