Dear @pontusoim, thanks for the update!
As you can see here, your board uses the following audio device:
If we go back to the Audio (Linux) | Toradex Developer Center page, you can see that it’s linked to the codec on the Verdin Development Board. Therefore, you may be using the wrong device tree. Thus, the audio interface on Dahlia will not work as expected.
So, regarding your questions:
On the Dahlia, there are two USB-C Ports. You shall connect the port referred to as Debug and you can connect to serial using, for instance, picocom on /dev/ttyUSB3. Then, when the system start to boot you need to interrupt the boot console.
However, as you’re using Torizon, there is an easier solution.
If you’re using the build command, you can set the desired device tree, i.e., imx8mm-verdin-wifi-dahlia.dts on the device-tree custom field. Then, all your images will have the right device tree.
Can you please give it a try?
Best regards,
Guilherme