Unable to boot 2015 iMac from external SSD with APFS + Catalina
My mid-2015 iMac's internal drive is dead.
I got an external SSD (SanDisk Portable) and created a bootable copy of Catalina - APFS format , using my laptop (2019 MacBook Pro). I can boot my laptop from this SSD bootable copy fine.
But the 2015 iMac does not recognize the APFS SSD as a bootable drive. Command + R + Disk Utilities sees the drive but Startup Disk will not let me select it.
So then I created another partition on the SSD, formatted as MacOS Extended Journaled and installed a bootable copy of Yosemite. The iMac can boot from this!
Question: Is there any way to make my mid 2015 iMac (no functioning internal drive) boot from an APFS external SSD?