Currently we are using keycloack as an identity provider in one of our applications

But have a requirement to have a custom registration single page, and I was looking around how to get the client URL or the current client URL from in the template of the login page of keycloak.

Well the solution for this is just really simple:

 href="${client.baseUrl}/register"

You can add the href to the tag, so it redirects to the custom page that you want to handle the registration or anything else.