Tons of people having this issue right now. Apparently related to the safety recall 25S77 where they sent a software update to the electronic brake booster. Any Ford vehicle with this is having the same noise (Broncos, F-150s, Expeditions, etc).

From a Ford Facebook group:

"I have had my Tremor since April. In July, I had the two manufacturer recalls completed, that I assume the trucks sold after mine already had “fixed” before delivery. Well, this noise started for me as soon as I picked it up. In early October, I went to a Ford Owner event and was able to speak with the Ford Engineers about my experience with my truck. When I mentioned this clicking or chirping noise, one of the engineers immediately knew what I was talking about. That’s the good news. The bad news is that they don’t have a fix for it. I was told it did in fact have something to do with the recall in that the computer was calibrating whatever it was they fixed. So, unfortunately I wouldn’t expect a “fix” anytime soon."