Audio DAC shim on RPi-5 with Ubuntu

I am trying to get system audio line output on a Raspberry Pi 5 running Ubuntu 23.10 by using a Pimoroni Audio DAC Shim.

Running Raspberry Pi OS (Bookworm) on the same hardware works as expected, with audio coming out of the DAC Shim, configured per instructions, when the DAC is selected in the Sound Output pull-down selection. So, hardware and connections are good.

Using the same configuration instructions on Ubuntu 23.10 (fully updated) has no audio out, the DAC does not appear in the Sound Output pull-down selector. Audio continues to be routed to the HDMI cable.

Does anyone have ideas or suggestions as to how to get this working?

Could be that Ubuntu does not provide the necessary driver-module. You could try to run sudo lsmod on PiOS and Ubuntu and compare the output.

Thank you.
Yes, there are differences in the kernel modules loaded.
RPi OS, loads an extra module called “designware_i2s”, which Ubuntu does not
I’ll have to go sort through that.

Interesting… I have never seen that one, but the i2s in the name does make it a good candidate.