SOLVED: This was a case of user error. I selected the wrong board and that was why the BlinkRGB example sketch wasn’t found and why I had the compilation errors. Once I selected the correct board, both of this issues went away.
I got an ESP32-C6 board a few weeks ago, installed Arduino 2.3.4 and downloaded the BlinkRGB sketch and ran it successfully. Later I got a notification about updated libraries being available so I installed them and now my sketch is no longer compiling.
I see compilation errors about RGB_BUILTIN is not declared in this scope and when I looked for the BlinkRGB sketch as detailed in the Arduino Examples ESP32-C6 page, I don’t see it present now (only FunctionalInterrupt and GPIOInterrupt are listed).