Thanks Peter, yeah, I just added the redirect URL via oc edit oauthclient/cockpit-oauth-client
Now I have the same issue mentioned in thread "Issue with configuring cockpit in openshift cluster" - MESSAGE: cockpit-protocol: couldn't read from connection: Error receiving data: Connection reset by peer
and the webpage returns Disconnected Server has closed the connection.
I've added G_MESSAGES_DEBUG=all, but don't see anything interesting. Is there something I should search for?