A Raspberry Pi can boot from an SD card, so why not a Mac Mini? Actually, it CAN. I successfully installed Catalina on an SD card and booted from the SD card. (Not the Catalina installer, the actual installation, like a hard drive) Yes, it is slower than dog slow, but it works. I tried to do the same with Ubuntu. I put a Ubuntu installer on a flash drive, and after booting the flash drive, the Ubuntu Live environment does not see the SD card hardware. Any ideas?