I am looking at docker images for ParaviewWeb. The documention refers to this dockerhub repository but it looks outdated (latest version is 5.8): Docker Hub
Is there another repository or should we build the docker ourself?
That is the correct spot. We are just manually building those images and we did not push a new one for 5.9. On the other hand, 5.9 had an issue with the Web due to some issue when handling so python dependency/dependency.
You should be able to build your own image using master (the 5.9 issue has been solved) using those image definitions here (PV) and here (Web)