If anybody is curious, here are the details on how to do that: https://www.pdq.com/blog/how-to-block-the-windows-11-upgrade/

If you want to take it a step further, write a Powershell script that checks that the registry entry is what you want it to be, and then changes it if it is not. Then create a scheduled task to run at login that runs the script. That way if/when Microsoft pushes an update that switches the registry entry back, the scheduled task will flip it back after installing updates/rebooting/logging in.

I am currently fighting this battle with New Outlook in Win 11 23H2. It's really annoying. I can get rid of it with registry entries, but when windows does updates it reverts the registry changes back. So scheduled task it is. It would be great if there was an Intune configuration profile to deal with this, but that would go against Microsoft's current methods of shoving new products down your throat.