DNN 9 doesn't have a nice UI 😟 so you'll need to use some SQL

  1. Go to the System Settings > SQL Console
  2. Run the following script
  3. Afterwards, restart DNN to load the setting you just changed

The Script

UPDATE PortalSettings SET SettingValue = 'False' 
WHERE (SettingName = 'EnablePopUps') 
And PortalId = 0

Change the PortalID to your PortalID, or remove the AND line to set it for all portals