Seeed Studio provides various technical details including Schematics and various guides on their Wiki page. The same page also contains details instructions on how to set up Arduino IDE for the XIAO ...

Works with MAX98357A (3 Watt amplifier with DAC), connected three lines (DOUT, BLCK, LRC) to I2S. For stereo are two MAX98357A necessary. AudioI2S works with UDA1334A (Adafruit I2S Stereo Decoder ...