If it's one of those and class compliant, you might be able to access all of it through alsamixer or one of the many frontends (maybe too many, maybe one for you): https://en.wikipedia.org/wiki/Alsamixer

The Audient situation appears to be a proper nightmare realm with non-class compliant stuff, but there is a tool with a list of caveats longer than you might want to deal with: https://github.com/TheOnlyJoey/MixiD

It's more best case scenario as an escape hatch and less problem solved, but it's something.