What kind of audio output exactly? How many? A hardwired headphone jack (of which there are various type) would take up space and be useless to many users. Mic

What kind of audio output exactly? How many? A hardwired headphone jack (of which there are various type) would take up space and be useless to many users. Microcontroller-based audio projects often use i2s for audio. Some don't output anything and just listen.