After updating to the latest version of Discourse, Yusa_Arifki is experiencing issues with the LDAP plugin. Despite disabling the plugin, the LDAP login button remains functional. Canapin identified the plugin being used as discourse-ldap-auth from GitHub. Canapin suggested contacting the author directly, as it’s an unofficial plugin. JammyDodger mentioned that Benjamin_D and jonmbake previously fixed issues with the plugin and might be able to help again. Benjamin_D provided a code snippet indicating that the plugin’s enabled? method relies on SiteSetting.ldap_enabled, which might be causing the issue.
I didn’t find it in Customization > Plugin. It’s unofficial. I suggest you to contact the author directly, but maybe someone who also use it will have an idea here.