Re: {Facepalm} 'Get Windows 11' nags in Windows 10 21H2, have started.
Yup.
And, once again, Internet to the rescue :
Disable Windows 11 Upgrade Using DisableOSUpgrade Registry Key
1. Type regedit in RUN or Start search box and press Enter. It’ll open Registry Editor.
2. Now go to following key:
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows
3. Create a new key under Windows key and set its name as WindowsUpdate. If the key is already present, skip to next step.
4. Now in right-side pane, create a new DWORD DisableOSUpgrade and set its value to 1