I'm not sure if this is a "buy a box" issue, a "buy a better cable" issue, or "you're SOL". I have a desktop computer with a couple of audio input jacks (a mic jack and a line-in jack; nothing special ...

The new Shure MV7i has a combo XLR/TRS input for a second mic or instrument. There's no need for a separate audio interface to combine the two signals. Is Shure’s MV7i the world’s first microphone ...