For what it's worth, you can also self host your runners without Ubicloud on Github. That doesn't remove other reasons to not run Gitlab, but it's also not unique. I've self hosted runners for a variety of reasons on Github with great success.
In a similar vein, using Gitea + self-hosted runners (including macos) here, very happy although we did do some of the work to make the "CI stack" (contributed back to gitea and act projects) so not totally batteries included yet. One thing that helps quite a bit imho is to avoid virtualization -- our approach is to run all CI jobs in containers, not VMs. Yes this has isolation implications, and requires some futzing to get docker-in-docker and docker-in-docker-in-docker to work (shout out to the Earthly team for figuring out how to host kind/k8s inside a container), but the "runs on any computer" property of containers (vs virtualization) is powerful. Want CI on your laptop? No problem. On a Windows machine? No problem.