@TOTOleHero said in How to use USB card (OTG) on Ubuntu touch?:

I want to use a USB sound card with Ubuntu touch ...

There have been no successful attempts reported to do what you are trying. Something about missing drivers or such. If you have the time and desire to dive into it, you could try.

My first guess would be to see of the card works on a PC installed with Ubuntu 20.04. And then try to find out what packages provide the necessary parts to get it to work. If it is a built in kernel module, then it might be a dead end for now.