Following along with this video, importing a 2.79 without the UI, I found the interface is in a different to shown here. The Load UI toggle is under a cog icon called Toggle Region (shortcut N) at the top right not below the Blender File.
I'm using release 2.82a. I thought it might just help someone else.
Yeah they changed the location when 2.82 got released if I remember correctly.
I’m not a fan of the change. I liked it better when it was in the Edit Preferences to be honest.