furthermore, dithering is an option?

void bt_app_a2d_data_cb(const uint8_t *data, uint32_t len)
{
size_t bytes_written;

#ifdef CONFIG_A2DP_SINK_OUTPUT_INTERNAL_DAC

uint16_t * pu16 = (uint16_t *)(data);
uint32_t cnt = len / sizeof(uint16_t);

while (cnt--)
{
*pu16 = 0x8000u ^ *pu16 ...

Great.

too much io_mux too complicated, sometime just need more pins as a general MCU.
PLAN IN THE FUTURE?