The search for the built-in LED - ESP32

A recent question for me from a reader of my ESP32 book (thanks Richard) was: how do I find out which pin the built-in LED (if there is one) is connected to? You'd think this would be a simple matter of consulting the documentation, but the documentation is very hard to find because there are so many different ESP32 development boards. They are often not even identified by a consistent name.…