There’s a clear list. And here it is.
MacOS Monterey hardware compatibility list
iMac - Late 2015 and lateriMac Pro - 2017 and laterMacBook - Early 2016 and laterMacBook Air - Early 2015 and laterMacBook Pro - Early 2015 and laterMac Pro - Late 2013 and laterMac mini - Late 2014 and later
That’s it. Some features of the new release won’t be available to Intel-based Macs, but the list of features is small and hardly going to get many Mac users clutching at their pearls. This does mean that it’s the end of the line for some Macs running MacOS Big Sur. If you’re running one of these Macs, the end of the road is nigh.
iMac - Mid and Late 2014 and Early 2015 MacBook Air - Mid 2013 and Early 2014MacBook Pro - Late 2013 and Mid 2014MacBook - Early 2015