The STM32 is converting I2S to SPI because it's a spare part & its USB interface is too slow to go up to the future plan of 4 channels, 96khz, 24 bits, but there already are chips which bridge USB to I2S.  If those were spare parts, they would be used.  The internet shows items which only go to 2 channels, 48khz, 16 bits.  Going higher would require a microcontroller with a higher speed USB chip.

Otherwise, the raspberry pi zero W showed its true colors with the failure of its BCM4343 chip.  The internet says many others have experienced sudden failures of the BRCM 4343.  The fragileness of it makes it less appealing.

The very latest method for getting the zero W to be an access point:

https://albeec13.github.io/2017/09/26/raspberry-pi-zero-w-simultaneous-ap-and-managed-mode-wifi/

Mercifully, this has gone from completely obscure 5 years ago to something everyone is doing, nowadays.