I've sysadmin'd all OSs for many years, but I'm with GP: I see Apple as another Microsoft these days (especially given MSs dubious push into non Foss oss) Hell even their efi implementation is non standard, and I really think people should pay more attention to Richard Stallman...(paraphrasing)
"Apple puts the user in a prison. It is a beautiful prison though".
Now, that's not to be defending others that do the same but in a different way (android is crap due to unrootable devices)...
Once again, the four freedoms as explained by RMS are the crux of the matter. The man was and is right, and it gets tiring seeing so many people bandwagon onto attacks against his person without addressing his position, for which I will always consider him a man who saw the future far before anyone else, and is getting more and more relevant every day.
This is a mischaracterizsation. You can boot Linux, it is up to Linux to have driver support for the T2 SSD controller so that it can detect it as storage.
That can be turned down to either accept any OS that was ever signed by Apple, or to boot whatever you want it to.
The third option should let you attempt to boot Linux, but like you said, whether the driver support exists is another matter entirely.
Startup Security Utility -> Secure Boot -> No Security
But there is a danger in this type of "democracy", namely that we're heading for a future where true general purpose computing starts to disappear, and universities and computing enthousiasts have to pay thousands of dollars for a universally programmable computer. With Apple aggressively vertically integrating their supply-chain, and others copying Apple's business tactics, the writing is on the wall ...
I think just the opposite happened. All we had were general purpose computers, then we added "easy to use" computers in the form of smartphones and tablets. It just allowed a lot more people to take advantage of computers, it did not remove access to general purpose computers for the rest of us. Personally, I love the idea of a bifurcated world where the less technically savvy use devices that are far more restricted and secure. I really like that my parents can get a device, like an iPad, that does everything they need from a computer (email, facebook, light web browsing) without having to worry about malware.
As for my computer, I use a Mac mini that dual boots macOS and Linux. I have an older Mac mini that runs OpenBSD exclusively. I also have a media server I cobbled together from scavenged x86 parts.
I'm not a programmer, but it's my understanding from this community and others I frequent that Macs make for a comfortable and useful platform for their work and leisure computing life.
So, despite your attempt at gatekeeping, Apple products do have a place in a random hacker's workflow if that hacker decides he wants it; it's not up to you to decide what someone else uses and enjoys.