In the stock firmware (http://domino.io/firmware/pi/openwrt-domino-pi-1.3.bin) after installing glzt_i2s module I see activity on I2S bus.
When I build firmware from scratch, glzt_i2s module was installed but there were not activity on the bus.
I use GitHub - domino-team/openwrt-cc: openwrt CC with Domino/GL patches
and packages athplay and iis from GitHub - domino-team/domino-firmware: This is the firmware and source code for Domino