Microsoft announced recently that it would allow people on unsupported PCs to install Windows 11. However, such users may first have to agree to a formal pact that their PCs may not receive updates.
Microsoft has confirmed that running Windows 11 on M1 Macs using virtualization software such as Parallels Desktop is not supported. So if you run into an issue, Microsoft's isn't responsible.
Microsoft has started informing people running Windows 11 on unsupported hardware using the Insider Program that their PC is ineligible for the OS and that they should go back to Windows 10.
Microsoft has blocked the Windows 10 October 2018 Update for some Intel PCs due to problems caused by Intel's accidental release of display drivers which "turned on unsupported features in Windows".