Starting in 2018 the Macbook Pro includes a secure boot chip that prevents your Macbook from booting windows, linux, BSD, gentoo, Fedora, Atlas Supervisor, other Mac O/S/s on a usb, etc.
You CAN boot a 2018 2019 or 2020 Macbook Pro from USB!
But it does take a few steps to get there.
Boot into Recovery Mode
To access Recovery Mode, turn off your Macbook, turn it on and hold the Command (⌘) and R keys. Keep holding them through the chime sound until you see the Recovery Screen below…
Click on Utlities (on the menu bar at the top of the screen, don’t click on Disk Utlities in the middle of the screen)
Select ‘Startup Security Utility’ and you’ll get this screen…
Change the settings for both to the same as the image above.
Secure Boot to No Security
External Boot to Allow booting from external media
Exit out, shut down the laptop.
Plug in your bootable USB device and boot up your 2018 2019 Macbook Pro from USB, hold the Command (⌘) key and you’ll see the startup disk screen, select the USB and boot it up.
Caveats, notes and disclaimers.
- You may not have any access to the internal drive. Not sure if it is a linux driver issue or some sort of on chip security, but so far, no access.
- Leaving ‘external boot allowed’ is a risk that if stolen, someone might be able to access the internal drive.
- The law of unintended consequences. Apple rarely supports playing around with bootable O/Ss, you could brick an extremely expensive device.
- Apple does have further detail on the T2 security chip and how to use it. Read more before playing around too much in there.