OK, so I think I have figured out how to make Mozzi sound through the internal speaker.
In AudioConfigESP32.h change these lines to:
// Set output mode
#define ESP32_AUDIO_OUT_MODE PT8211_DAC
// For external I2S output, only: I2S_PINS
#define ESP32_I2S_BCK_PIN 12
#define ESP32_I2S_WS_PIN 0
#define ESP32_I2S_DATA_PIN 2
It seems to work, even though the Core2 uses the NS4168 I2S amp.
In your code, put this at the top:
obviously, and in the setup():
in the updateControl() function.
Also, in the Arduino IDE, set PSRAM: Disable.