My new Pi 4 was not able to sniff packets from other devices on wifi with Raspbian. I installed Ubuntu 20.04 and got same problem. The only traffic I could see was that which related to the Pi itself, plus some broadcast traffic.

After reading up on nexmon I installed Kali, which I understand has the nexmon patches included. But that has still not resolved the problem.

Has anyone been able to get Kali (or any other linux, for that matter), working on Pi 4, in either promiscuous or monitor mode, over WiFi?