I wanted my audio out the rear instead of the front where the expansion cards are. I purchased a dongle with the same chipset as the Framework audio expansion, the Conexant CX31993 USB audio CODEC (source: What's inside the audio expansion card? - #15 by nrp ).
My microphone works with this expansion card. I updated to kernel 6.17.7 since my first post, but everything else is the same, still running NixOS unstable with pulse audio.