Pagure can use the Openid federated authentication protocol.
You can use any OpenID-compatible identity provider to provide login with whatever backend you prefer, for example LDAP.

Yes. Unless that openid is quite old.. OpenID Connect would be more useful (there are great projects like dex for this).

We're using https://pagure.io/ipsilon/ which provides an number of backend including LDAP and exposes a number of protocols including OpenID (which is old maybe, but it works doesn't it? Age seems like a poor counter-argument) and OpenID Connect (but also SAML, and used to do persona).

So I don't think there are any plans to support LDAP directly in pagure (though if someone wanted to contribute one we would look into it) and I was advice people to look into ipsilon if they wish to integrate pagure with a LDAP.

Yes I know. And actually I do not think that the value is about whether or not we we should support ldap, I think it would be more useful to support a reverse proxy that could do the auth (and then rely on http headers). That way you are not dependent on what is behind this proxy.