I too have this problem. Keycloak 17.0.0 in a Docker container behind Nginx (also in a Docker container) worked fine, but since then every release has caused me problems with the admin console (see http://keycloak.discourse.group/t/keycloak-17-admin-console-shows-only-the-top-navigation-bar/14695
I think the change in behaviour is down to this commit https://github.com/keycloak/keycloak/commit/3da5a8ea7349ee306895f0071b883901102fe2fd
So I suspect the problem in my case is down to me not finding a working combination of Nginx and Keycloak configuration settings.
BTW every other Keycloak function in my environment works just fine on 17.0.0 and all versions through to and including 19.0.1 — only the Admin console does not load as expected.