Working with Kerberos authentication

I have a running instance of Nextcloud on a server machine, and i’m trying to get it to work with Kerberos authentication, so i installed the mod_auth_kerb on apache2, the SAML and SSO app on nextcloud and tried to setup as the official tutorial says so.
Since there is only one tutorial on the web about this (the official one), i decided to call for help here.
Here’s the problem, after enabling the app on Nextcloud interface and choosing to use the Environment Variable for authentication, it should ask me which variable to use, but it doesn’t. It asks the “Attribute to map UID to”, and after that it changes to an interface identical to the SAML setup.
Has anyone actually got it working with Kerberos??
If so, what am i doing wrong?
I also set the Location field on nextcloud’s apache config file, as the guide says, on the “/index.php/login”, and nothing seems to have changed, nor the logs presented something unusual.
Any thoughts on this?