Concourse
Concourse was my first selfhosted CI/CD tool, disliking Gitlab CI/CD and Jenkins, i've tried Concourse. It's a pretty good tool, based on Yaml files, it's not that easy to use at first. I would recommend it to docker only projects, it's a pretty good tool for that. On the long run, i've switched to Tekton and dumped Concourse. But if you need a CI/CD and enjoin Docker, you should give it a try.