Apple recently announced their new MacBook Air with Retina display, which is a nice upgrade from older versions. Apparently it is impossible to boot with a Linux distribution on the new MacBook Air. This is because of the new T2 chip that manages Touch ID’s Secure Enclave, APFS storage encryption or UEFI Secure Boot validation.
Apple’s own T2 documentation says that support for booting to Linux is not available. Even the Microsoft Corporation UEFI CA 2011 certificate used also by Linux distributions isn’t trusted at this moment, so the T2 chip will make it impossible to boot from Linux distributions that use it. Only Windows is allowed to boot via Boot Camp at the moment.
On Apple’s Secure Boot support page it shows how the new “Startup Security Utility” can be used to disable Secure Boot, but some people have already tried this and tried to boot Linux and it did not work. So as of right now you are unable to boot to Linux on this machine as well as other Apple machines that include the T2 chip (Mac Mini, iMac Pro, MacBook Pro 2018).
Apple has yet to comment on this issue.