I was able to reinstall and reactivate it, and even add my personal iCloud account. And it's actually absurdly easy (install older version of OS with three App

I was able to reinstall and reactivate it, and even add my personal iCloud account. And it's actually absurdly easy (install older version of OS with three Apple DNS names blocked at your router/nameserver), then edit /etc/hosts similarly, and then you can upgrade all the way to Sonoma with everything functional, no alerts or warnings.