Since bcmon is limited to old Broadcom chips, consider these alternatives:

Bcmon is an legacy tool with specific hardware and software constraints: Bcmon - 4PDA

Bcmon is an incredible piece of Android hacking history, but it’s on modern phones. If you have an old Nexus 7 or Galaxy S3 lying around, revive it as a portable packet sniffer. For everything else, invest in an external Wi-Fi adapter.