Teensy LC, audio library support?

[PaulS]

But Teensy LC does have the I2S peripheral, and the audio library does have some limited support for Teensy LC. Even fairly simple audio systems quickly use up LC's limited CPU and memory.

Would it be possible to talk to the PT8211 DAC over I2S with a Teensy LC?
This small program compiles without error for Teensy LC but no sine output out of the PT8211 kit. This code does work on a Teensy 3.2.

// PT8211 bd    Teensy
// VCC          3V3
// GND          GND
// WS           23
// DIN          22
// BCK          9
// --           11 (MCLK)

#include <Audio.h>

uint32_t Freq = 440;

AudioSynthWaveformSine   sine1;
AudioOutputPT8211        pt8211_1;
AudioConnection          patchCord1(sine1, 0, pt8211_1, 0);
AudioConnection          patchCord2(sine1, 0, pt8211_1, 1);

String incoming;

void setup() {
  Serial.begin(115200);
  while (!Serial);                        // wait for serial monitor to be active
  Serial.setTimeout(50);                  // set timeout in millisecs for readString()

  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, HIGH);

  AudioMemory(12);
  sine1.frequency(Freq);
  sine1.amplitude(1.0);
}

void loop() {
  while (Serial.available()) {
    incoming = Serial.readString();         // read string from serial monitor until timeout
    Serial.print(incoming);                 // return input string to serial monitor
    int32_t value = incoming.toInt();       // convert string into number
    Serial.println(value);                  // return value to serial monitor
    sine1.frequency(value);                 // update frequency
  }
}

Looking into the MKL26Z64 datasheet, the I2S pins are available on the 48pin package:



From the Teensy LC schematic:
pin 33 connects to Teensy pin 15/A1
pin 34 connects to Teensy pin 22/A8
pin 35 connects to Teensy pin 23/A9
pin 36 connects to Teensy pin 9
pin 39 connects to Teensy pin 11


So electrically it seems possible to output I2S on a Teensy LC.
In which audio library files should I now have a look?

[Arduino 1.8.13, Teensyduino 1.53, Windows 10 Pro]

Thanks,
Paul