I use a mobile SSD installing Windows To Go as my mobile workspace. EFI boot works fine on many computers. Booting it on my Macbook also works fine until the installation of mac OS Mojave 10.14 Developer Beta2 . After that installation, I can still see "EFI Disk" while holding Option key during boot. But after select that, it just keep booting into macOS . I tried rebuilding EFI firmware, reinstall WTG but not working either. Select boot disk manually in Settings shows an error message "Bless tool cannot set the boot drive". I search for that issue and I found this discussion: https://www.zhihu.com/question/282032748 (In Chinese) Someone says that their Bootcamp Windows and Time Machine Disk cannot boot either in the Option menu. Someone even says that after wiping their Mac and reinstall OS X 10.12, WTG still not bootable. If that's true, I think maybe Apple changed their SMC's firmware to prevent(?) third-party EFI systems from booting. I relied on WTG to get rid of Office for Mac's low performance while handling huge files. This issue is really annoying. I have the same concern as the question's holder on Zhihu: "I don't konw if it's a BUG or a Feature ."
I chose "Display connected devices" in Device Manager. The WTG Disk wasn’t linked to the Mac during the installation of 10.14, yet it functions properly on other systems after resolving this problem.
maybe but unlikely. your original post says people can't boot into their time machine disks either. that would be very odd if this is a new feature. to me this sounds either like a bug, or something corrupted in your firmware. both could be the case because you are running a beta operating system. there is a reason for the hefty disclaimers that come with using those.