There is already a blacksmith sh if you don't want to selfhost your runners. Or codeberg as a full solution if I am not mistaken.

+1 for Blacksmith. You need to have a Github org to use it as it won't work on personal accounts, but it feels like a magic want that just makes runners 2x as fast.

I have it for all my stuff (dozens of repos and hundreds of PRs/builds per week) and it's only once in the last year that I've exceeded the free resource levels. I don't know if it's just extra capacity or they're burning VC dollars in the hopes of inspiring posts like this, but either way I feel like I'm taking advantage of them at this point.

But doesn't Blacksmith piggy back off of the Github Actions control plane? Outages will just spread to Blacksmith

Codeberg only allows F/LOSS software, for most companies that's a dealbreaker.

Private projects usually are not owned by companies

Your proprietary personal hobby project doesn't need an entire publicly-accessible Forge, it can just live on your local drive or home server. It is also not critical enough that GitHub occasionally being down is a big deal.

If you're looking for a publicly-accessible Forge SaaS for your private repos and are willing to pay for it, you are almost certainly a company developing proprietary software.