Yes about sign : drivers which were used as bases of our omega simpleaudio driver seemed S16 as normal but if Andrew is sure it actually sends unsigned then that is the problem :
If the maxxxxxx driver actually uses the unsigned (weird unstandart and rare) 16bit format then we need to switch our firmware to builds using an asoc/alsa wm8960 or pcm5102 or whatever else is available as nearly ALL OTHER i2s drivers would provide us the usual/standart (i2s meaning signed) our DAC chips need.

"MCK lack" subject is not the problem here because I also use a i2s DAC chip that features an MCK generation builtin because MT7688 chip does not have any MCKout.

These 2 matter would make me much regret the former ar9331 soc chip...