The amount of time I need to spend maintaining my Forgejo instance this year, even after accounting for this RCE, has been less than the amount of time GitHub has been degraded or unavailable this year.

That doesn't match my experience at all. I had a Foregjo instance on a Raspberry Pi, and maybe it's typical SD card issues, but the number of times that Forgejo has crashed because it locked its own database and couldn't continue and the number of times repos I mirror from GitHub just mysteriously stop syncing is quite probably the same number of times GitHub has been down this year.