> - upgrading to Catalina via USB installation image. If the OS image is jumping several versions (or actually being downgraded from a security patch release),

> - upgrading to Catalina via USB installation image. If the OS image is jumping several versions (or actually being downgraded from a security patch release), here be dragons. Typically the USB installer pulls down another installer via Wi-Fi and then has to perform a random "this disk needs an upgrade" routine which 50% of the time results in bad thing happening and I'd be left with the flashing question mark. Then its time to start over again. Weird. I had the opposite problem. Mid 2012 Macbook, couldn't get El Capitan to install at all, but installing directly to Catalina from the USB worked first try.