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Thanks in advance for any help...
 
I have to downgrade Big Sur macs when my company receives them, after creating admin profile I boot to recovery, erase the drive, then boot to a catalina USB stick for install.
 
I've tried multiple wipes / re-installs, even from the Network via Apple, but now the machine will start to boot, fan kicks on high for like one second, then crash and reboot.
Sometimes I just get a white "ghostbusters" symbol.
 
I'm wondering if the newer hardware is choking on the older OS, like maybe specific firmware for Big Sur is present, now since it is trying to load catalina it is just crashing?
 
Any ideas?

Hey Scott,

The "ghostbusters" icon you mentioned is defined in the following apple document:

https://support.apple.com/en-us/HT210901

"A prohibitory symbol, which looks like a circle with a line or slash through it, means that your startup disk contains a Mac operating system, but it's not a version or build of macOS that your Mac can use."

During these tests are you able to successfully format the disk and install macOS Big Sur on said disk? Apple mentions how to do that here: https://support.apple.com/guide/mac-help/erase-and-reinstall-macos-mh27903/mac

Like you had mentioned, it could be a case where the Mac can't downgrade to Catalina. Are these M1 Macs? If so, it sounds like downgrading to Catalina may not be possible:

https://www.macworld.co.uk/how-to/can-m1-macs-run-old-macos-3802190/#:~:text=Can%20M1%20Macs%20run%20macOS,compatible%20with%20Apple's%20new%20processors.

Hopefully these thoughts and info help!

Thanks for your reply, it was an intel mac that came with Big Sur.

At least perhaps my thought process is at least going down the right path logically...

I really appreciate your reply.

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