It sounds like you'd be better off self-hosting Jenkins. The other issue with GHA is they cap all runs at 6 hours.
Despite what people say about "maintaining" Jenkins (whatever that means to them personally) - you can set it up in an IaaC way including the jobs. You can migrate/create jobs en masse via its API (I did this about 10 years ago for a large US company converting from what was then called TFS)
Despite what people say about "maintaining" Jenkins (whatever that means to them personally) - you can set it up in an IaaC way including the jobs. You can migrate/create jobs en masse via its API (I did this about 10 years ago for a large US company converting from what was then called TFS)