Given the fact that there are applications that are yet to be updated to be compatible with MacOS Big Sur, quite a few people saw a need to downgrade back to their older MacOS versions.
I will discuss how to create an external USB bootable drive for multiple MacOS versions and how to use this drive including on systems which have a T2 chip on them.
The Apple support links are as follows:
https://support.apple.com/en-us/HT211683
https://support.apple.com/en-us/HT201372
The free archiver Keka can be found at:
Let’s see how this works…
Nitin Chandra's Blog 