Just needed that recently,
Link Preview Image GitHub - wzrdtales/nodebb-plugin-ldap-override: a nodebb plugin that works on the latest versions and completely replaces the default login with an ldap onea nodebb plugin that works on the latest versions and completely replaces the default login with an ldap one - wzrdtales/nodebb-plugin-ldap-override
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But note that this is a complete override of the default login, the nodebb internal accounts are not going to work anymore.