My parents 2012 Mac Mini is running High Sierra off of external SSD Drive. I was able to install High Sierra on it fine, and have experienced brio problems with the setup. I run CCC wo backup the computer very night, and may have had to clone the current SSD drive from a backup. When I attempt to install Mojave to I get n error messages that it cant install Mojave to the SSD drive because it does not have a Firmware Partition? But I did get High Sierra installed it a few months ago, and also have Mojave running off another headless mac mini booting off a SSD drive. So I was able to get Mojave to install and run off an extren usb ssd drive. I tried reinstalling High Sierra from the recovery portion, and got the same "disk needs a firmware portion" message. Any suggestion? The machine are not usable w/o OSX running off of a SSD drive.