internal nextcloud user “admin” has all privileges. Domain admins, doesn’t have them by default.
runagent -m nextcloud1 occ user:info admin
runagent -m nextcloud1 occ user:enable admin
runagent -m nextcloud1 occ user:resetpassword admin
Replace nextcloud1 with your nextcloud app instance id.
On one of the screenshots above I see “builtin administrator user (…” but I believe that user comes from AD/LDAP (you can check it against your domain user’s Display Name or what is between the parenthesis). The admin user menu shows up like:
