I don't have data for it, but I have been a Github user since 2012 and have found it to be down often for pretty much that entire time. I always figured it's cultural to a degree–new features always seem pretty buggy/underbaked, and often continue to long term but remain unloved and incomplete.

I has never been so bad as in the couple last years. And it's getting worse.

I never had to wonder if Steam is going to be working today, so I could play my game after work, but it's been an issue with GitHub since covid. At least for me.

Fortunately, due the nature of the service, I can sit out most downtimes. Most of the time at least.