I am using Audacity 2.2.2 on macOS High Sierra version 10.13.5
I am trying to record from a Dansrue Super USB Cassette Capture and it Audacity will not give me an option to switch from Built-In Microphone to a device using USB.
Ensure that you connect the USB device before you launch Audacity.
Please look at the advice on this page.
If this is similar to other devices of it’s ilk, it will show up in the Mac System Preferences / Sound / Input as a PnP Audio Device. You may need to insert a cassette and start it playing in order for it to show up.
– Bill