Clean install Catalina to i7 macbook help

[ell]

Hi, a little stumped here. I have a 2019 macbook pro with an intel i7, with T2 chip. The client wants to roll back from big sur to catalina. Fine, I uncheck all secure boot options, theres no password on the firmware. I plug in my multi partitioned sata drive with all osx versions to it via my usb3>usb-c adapter and none of them show. I try boot to recovery and select startup discs, still no show. Reset the PRAM. Finally I make a flash drive with catalina. Boot to it, from options and I get the dreaded circle with a slash. Ideas?

 

[mmerry]

Assuming they have a backup of all they data. Maybe do an internet recovery.

Other macOS installation options​

When you install macOS from Recovery, you get the current version of the most recently installed macOS, with some exceptions:

• On an Intel-based Mac: If you use Shift-Option-Command-R during startup, you're offered the macOS that came with your Mac, or the closest version still available.

 

[ell]

Hey, great trick! thanks so much!