Dynamically set Client URLs on Keycloak Startup

Question

In Keycloak there is already a way to export the whole realm with all clients, users, roles etc. This results in a file that can be used to import that realm during keycloak startup. This works like a charm, but the problem is that the URLs of the clients in keycloak are hardcoded, in my case to localhost.

I'm looking for a way to set the Base URLs of the clients dynamically, in order to deploy keycloak with an imported realm and everything works out of the box. Unfortunately, Keycloak doesnt seem to allow environment variables in the client configuration using the Keycloak Admin Dashboard. As a consequence, using environment variables in the realm-export.json itself is also not allowed :/

The docker container of keycloak (jboss/keycloak) does not even have envsubst. Its really frustrating to already have a json file that does most of the configuration at container startup when I still have to manually configure the client URLs afterwards.

Any solution? Thanks in advance.