> The average person on the street who wants to install or try out Linux must be able to find it as well.
The average person on the street is not going to compile their own kernel; they're going to download a halfway-popular distro from somewhere. (Honestly, anyone who can figure out `make menuconfig` can figure out the UEFI menus.) So the question is whether Microsoft _signs_ all the halfway-popular distros' Linux kernels / bootloaders, not whether Secure Boot can be disabled. And in practice, they have signed those bootloaders, so I'm not sure what the problem is here.
That said, if Microsoft refused to sign Linux kernels, that would definitely be grounds in my eyes for a serious antitrust complaint.