I agree with a lot of the sentiment here, but I want to make one important correction: Apple has helped us. In particular, they gave us access to DTKs for the M1 and provided us with a liaison for the migration. We're very thankful for that help.
That being said, Apple is a massive company and they have their own development goals and velocity for macOS. They're not actively looking to break Homebrew, but they're also not going to halt everything for us.
More than one person just last week got stuck in a loop where the system wants credentials for your old deactivated Apple ID. The solution isn't hard but the UX flow fucking sucks.
You must manually sign out of all devices using your old ID and sign in again. Except before you can do that you have to disable Find My. With the deactivated credentials again.
It shows the OLD email and wants the old password but you have to actually enter the NEW password in the dialogue so Find My deactivates and you can sign out.
The thing is efforts like homebrew is basically the only thing that keeps Apple platforms as a viable developer's platform (without it it'd be intolerable, as Apple has zero official solutions for managing software not coming in pointy-clicky Appstore packaging) - and given that macs are still popular among many developers, it's a mystery why Apple corporate pays so little attention to it. It's like they sold a car without any tires and wouldn't even acknowledge the existence of tire manufacturers, let alone how vital they are for the actual users of the product.