I don't know about GitHub or GitLab, but in my entire professional career, I think my total downtime due to failures in locally hosted Git repos is zero. Likewise I don't recall ever having a problem due to locally hosted bug trackers or code review systems. This stuff isn't hard, and we've been able to do it reliably for a very long time.
What certainly has wasted a horrible amount of my time in recent years is working around build systems and package managers that are so badly designed that not only do they have a dependency on some online repository in the first instance, they also make it difficult or impossible to download and cache those dependencies in a supported way so that you can have 100% reproducible builds with nothing but locally hosted resources. Surely this is just about the most basic requirement for a robust software development process?
Since you're looking to collect anecdata, I've had 100% uptime from my self-hosted GitLab instance, which has been online for about a year. GitHub may be on par with that, but it's hard to beat 100%.
I self host my gitlab and when there's an update it goes down for several minutes (well actually I don't know if it's unusable, haven't tried, but with the backup and the updates, it's long)
I'm the only one working on it, so that's not a problem for me.
I must have transposed "unexpected" downtime in my head. Yes, I update the box and installation periodically, and yeah, that is time that my GitLab environment is not available, so I guess it's not 100%, but like you I am the only person using it, so it's effectively 100%
What certainly has wasted a horrible amount of my time in recent years is working around build systems and package managers that are so badly designed that not only do they have a dependency on some online repository in the first instance, they also make it difficult or impossible to download and cache those dependencies in a supported way so that you can have 100% reproducible builds with nothing but locally hosted resources. Surely this is just about the most basic requirement for a robust software development process?