Sounds like I am the only owner with this symptom. Have been in contact with Jeep customer service and they aren't sure what is causing the noise. No fault codes are appearing and the Jeep performs as expected. No use issues or any other symptoms besides the alarm noise.
Jeep offered to give me a loaner while the dealer diagnoses but I know they are going to start taking stuff apart and still may not find anything obvious. So we decided to wait and see if any symptoms develop.
I can reproduce the noise on demand now so that is something. However, the process is basically to park the vehicle and come back several hours later and force the Uconnect app to refresh. During that process, the modules wake up and then I can hear the sound......barely audible from outside the locked Jeep. Can also produce the noise by parking the Jeep and coming back later and plugging in.
So, waking up the modules creates the sound. Maybe they are grouchy when first awoken? My daughter is like that. Don't even think about having a conversation with her until after her first cup of coffee.