I am aware that this TOH won't happen anytime soon. But still, out of curiosity: What was your idea to achieve that. Neither I2C nor NFC are a good choice for Audio transmitting, are they? Thanks!
I2C have nothing to do with audio.
I2S is for audio.
Sending stereo audio over I2C, at a limited 400K, will be a real PITA. Some compression/decompression must be done between TOH and Jolla.
There is also high speed I2C at 5Meg but Jolla support up to 400K.
Sorry, but sound quality will be very poor.