Hi. Apologies for the delayed response but for some reason I didn't receive a notification about this post.
You can use pretty much any source code repository -- hosted or local -- with IC2 as long as it's supported by the underlying JetBrains IDE:
While I use BitBucket for IC2 itself -- something that's actually more historical, though I do like BitBucket overall -- I actually use GitHub for almost all of my other projects including personal projects,
IcApexDoc,
sirono-common, etc. The only real advantage of GitHub over other Git repo providers would be more first-class support in the IDE for pull requests, though I think that perhaps the GitLab IDE integration now supports similar (don't quote me on that).
As for the CI/CD aspects, I don't know that there's any real difference between what the various providers have to offer from an IDE perspective. All of them use standard VCS/Git hooks/triggers to have CI/CD pipelines execute automatically in response to commits on various branches, and that occurs outside of the IDE for the most part. There may be plugins for the IDE that allow you to integrate some aspects of those pipelines more directly. If so, I haven't used them and can't comment on them unfortunately.
I don't know if that's helpful or not. I'm happy to answer additional questions to the best of my ability, though.
Regards,
Scott Wells