I currently have 4 boards active.
Sometimes none show up, mostly one, and sometimes all four.
But in “Bonjour Browser”, found on Bonjour Browser for Windows, I see all 4 ESP8266, in addition to the other services like google home and tradfri gateway. So the arduino UI must be buggy picking up the ESP announcements. It would be nice to be able to enter the addresses of the ESP’s instead of waiting for the Bonjour protocol