Yes, it’s built using Grails 3.3.10 which requires JDK8. I use SDKMAN! to manage my JDKs so I can have multiple JDKs on my machine and use the old ones for this system https://sdkman.io/
The idea is to migrate to Grails 5+ which supports newer versions of JDK but won’t be any time soon since that requires a lot of code migration and testing and I’m the only maintainer of EHRServer. Though help is always welcome!
It is also possible to create a docker image and build it there then use that WAR for docker-compose. That was the idea of the Dockerfile.dev that are on the repo. There are a couple of those but since I’m not a docker expert, I don’t know if those are “correct”, I somehow managed to build grails there and run it with an external DB.