That Apple blocks you from running every program you put onto it until/unless it can be properly certified, and that “Big Sur can bypass any firewall restrictions the end-user attempts to create”? It’s true that it’s not nearly as bad as it may sound at first, and they even released a statement that:
We do not use data from these checks to learn what individual users are launching or running on their devices.
Notarization checks if the app contains known malware using an encrypted connection that is resilient to server failures.
These security checks have never included the user’s Apple ID or the identity of their device. To further protect privacy, we have stopped logging IP addresses associated with Developer ID certificate checks, and we will ensure that any collected IP addresses are removed from logs.
Though I also understand that if someone wants the ultimate in privacy, it’s difficult to trust such a corporate promise, especially one like Apple known to hide or lie about such things. (Edit: also… “developer ID certificate checks”, so if you don’t register with Apple as a known developer then…?)
I still use Mac OSX myself, but if someone wants to avoid that and use Linux for this reason, I’m not going to argue with them - whereas I would push back a little bit if a friend were to tell me they planned to put Windows (as the primary OS) onto a machine.