If you're in Windows 11 Dev Channel then you have to clean install back to Windows 10 to totally exit Insider Program. Unless you went from Windows 10 to Windows 11 in the last ten days, then you can go back to Windows 10 through the Go Back option in Windows Update, Advanced Options, Recovery, Go Back then from there either go into the Release Preview Channel or option to stop getting builds via "Unenroll this device when...". If Go Back is grayed out then you'll have to clean install back to Windows 10 if you're in the Dev Channel. If you're in the Beta Channel then go to Windows Update, Windows Insider Program, Stop Getting Builds and switch too "Unenroll this device when the next version of Windows releases." You'll still get Insider Builds into the next major Windows release. If that is grayed out, the next option (right under the one I just mentioned) is "Unenroll this device immediately" which will tell you to clean install back to Windows 10. Right now at the time of this post Microsoft is allowing a temporarily timeframe of allowing Insider Program participants that are in Dev Channel to go back down to the Beta Channel. Usually once you're in Dev you can't go back down to Beta. However if you did that you would still be in the Beta Channel getting Beta builds when they are released. If you want completely out of the Insider Program and not want any more builds at all and/or want to revert back to Windows 10 outside of the ten day grace period from when you upgraded to Windows 11 Insider Program then your only option is to clean install back to Windows 10. This link explains it in full: https://insider.windows.com/en-us/leave-program
Picture from my Windows 11:
