Big Sur downgrade and firmware

[camelia]

Hello,

rMBP 15" Mid 2014

Do I have to worry when macOS Big Sur updates my Firmware, now that I wanted to downgrade to macOS Mojave in a non Mac with T2 chip?

"Firmware, covering the firmware proper and Recovery tools, is updated to the latest version whenever a newer version of macOS is installed on any mounted disk, whether internal or external. Thus, if the internal disk has Catalina installed and you then install Big Sur on an external disk mounted on that Mac, both the firmware and Recovery software is updated to that supplied with Big Sur. This only happens at the time of installation"

Firmware and Recovery upgrades and downgrades on different Macs

What would happen to a Mac’s firmware if you installed Monterey beta to its internal or external disk? Could that be reversed?

eclecticlight.co

How to Downgrade BridgeOS on an Intel T2 Mac with Apple Configurator 2!

You can now downgrade BridgeOS on your Intel T2 Mac (2017-2020) to a previous version with an IPSW BridgeOS file & Apple Configurator 2!!!

mrmacintosh.com

Thanks
Camelia

 

[mikzn]

IMHO - I don't think apple would have a software - firmware update that would remove the option of installing the previous versions of macOS that were included with the original MBP's

An easy way to check? - install Mojave on an external Bootable drive - or if you have a Mojave clone try booting that Clone if it is on an external drive?

IMHO - a major issue - it is not easy to backward migrate data from Big Sur back to the Mojave version (especially hidden files in the "user library folder")

 

[BLUEDOG314]

You rarely if ever have to worry about firmware. The only thing that comes to mind immediately, when upgrading, was the move to APFS. You couldn't boot from an APFS formatted drive without first receiving an update. Going backwards is never a problem. I was playing around with a mid 2014 MBP a few months ago and wanted to see what 7 years of macOS updates felt like so I clean installed Mavericks on it. Worked fine besides being barely compatible with any apps.