I have an M1 Air, and I wanted to downgrade it to Big Sur (more specifically, 11.2.3). So I created a USB installer, tested it with my Intel machines, and they were able to boot into the installer USB just fine. When I plugged in said USB (just a regular USB-A flash drive with an adapter), it just wouldn't be acknowledged at all in the boot picker. Disk Utility does see it just fine, even saying that it's bootable, but none of the actual boot pickers see it (Startup Disk, holding down power, etc).
I thought this was an adapter issue, since they were pretty cheap, so I pulled out my USB-C flash drive, made that into an installer just like last time with the .app and the
createinstallmedia command... it works on the Intel machines again but it's the same thing with the M1. I even went as far as to nuke the Monterey install on the SSD in hopes that it'd have no other choice and have to boot into my installers... hahahaha, no, instead now I have only the Monterey recovery partition. Seemingly went through the whole internet for answers to find nothing at all.
It definitely can't be Apple preventing downgrades, right? After all, I've seen other people on Monterey downgrade to Big Sur just fine on their M1 machines... I heard about using .ipsws and Apple Configurator 2 but I don't have another Mac with a TB3 port nor a TB3 to TB3 cable. Can't be that it needs a specific M1 version of Big Sur since it's quite literally a .app...
I'm out of ideas, I gave up and am currently reinstalling Monterey, but any help to finally solve this weird mystery of mine is very well received! Apologies if anything's confusing, please do ask if that's the case since I'm writing this at 1AM still trying to figure out what's going on... Thanks in advance!