Of course the major distros like Ubuntu can boot with the default secure boot keys.
I have a feeling x86 manufactures would face considerable backlash if they tried to lock down SecureBoot in a manner where it's impossible to disable. (and yes, I do know there are some Microsoft devices that are already setup this way, but the majority of manufactures do allow control over SecureBoot). Then again we have Intel ME on all our machines and that's somehow still okay, so maybe you're right.