I’m running the official docker image and I get HTTP 404 error when trying http://localhost:9990/health or on port 8080 which is the one exposed in the docker image.
You need to add an argument to make the management interface listen to another adress than 127.0.0.1.
I tried with :
docker run -p8080:8080 -p9990:9990 quay.io/keycloak/keycloak:7.0.1 -Djboss.bind.address.management=0.0.0.0
In the next version, you should be able to enable some statistics with the env variable KEYCLOAK_STATISTICS and this should open the interface directly.
(non intended bonus : KEYCLOAK_STATISTICS=on should open the interface to 0.0.0.0 without enabling any statistics)