I read a number of posts about installing JACK to use a behringer USB audio interface. I wanted to post this here because I could not find this information otherwise. Jack is not necessary to get this working at a basic level with Audacity. YMMV if you want to do something more complex, like multi-track recording. But the Behringer U-Phoria UM2 is a single channel (stereo) device – not gonna do much multitrack recording with this.
You’d need this amplified device in order to interface a studio-quality dynamic microphone with your computer. Without low-noise amplification, your stage type mic won’t be at the right levels for the audio input to your computer, and the computer’s input is also noisy.
Of course, you may find that you need jack for low-latency recording from this USB input device, however I was unsuccessful in figuring out all the things that need to be connected or whatnot in jack. After I uninstalled jack, I realized all you have to do to get this Behringer USB device working under Ubuntu 18.04 is to plug it into a USB port. Ubuntu talks to this device just fine without any further adieu.
TL:DR – Plug it in and go.