downgrade from Monterey 12.0.1 to Big Sur

I installed Monterey and immediately began having internet connection problems through both wifi and ethernet. I have worked through all the usual connection solutions. Please do not address this issue. I have taken to authorized service center and they agree there is an unknown issue relating to upgrade and that I should downgrade.

I want to downgrade to Big Sur but all the instructions are out of data from the beta era. In Recovery Mode the only option is Monterey from the internet (a clean install did not clear the problem) and RM refuses to recognize my Big Sur USB drive installer. This is a known issue (actually a choice on Apple's part) which is well documented. Further, Apple Configurator 2 clearly states that it cannot restore a Mac, which is apparently a recent change. Thus, all options (other than buying one of a handful of USB C drives which are said to be recognized by M1 Macs, are closed off to me, unless I am missing something. Would be happy to be corrected by someone who has actually downgraded from Monterey 12.0.1 (not the betas!!) using a viable method.