WAV library: https://www.xtronical.com/basics/audio/digitised-speech-sound-esp32-playing-wavs/

A github project that probably plays a wav file: https://github.com/LilyGO/TTGO-T8-ESP32

A micropython project playing WAV (though I'm quite sure I read somewhere that the internal DAC wasn't yet supported on micropyton): https://m5stack.hackster.io/lukasmaximus89/play-wav-files-on-your-m5stack-3bee7e

internal *ADC* code: https://github.com/espressif/esp-idf/commit/2fceec4d858c62a489496678c765ae1a2d68645c