How to track down the source of unknown device connection requests?

I have a ASUS ZenWifi ET8 router connected to a Starlink. I have set up MAC filtering (acceptance feature listing the only devices allowed on the WiFi). I am still getting random device connected messages from the router for random MACs in the range of 00:02:00… and 00:03:00… . How can I track down the source of these intrusion attempts? As a note, these MACs intrusions started after I installed a new DirecTV Genie C51-700 remote connected only to the DirecTV receiver's coax network. I have DirecTV blocked on the ASUS router side.

Question by Bruce on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.