It's not quite what you're asking for, but Jujutsu+Git is still a much better dev experience than Git alone and is completely compatible with those sites.

I use Jujutsu for 100% of my version control at my day job, where all of our repos are in Bitbucket and all my coworkers are using Git. AFAIK most of my coworkers don't even know I'm doing anything different, other than those who I've "evangelized" so far :)

...I think my PRs have gotten noticeably cleaner and easier to review, though!