The Scarlett 2i2 has XLR inputs at the back for microphones and 6.35 mm (1/4”) jack inputs on the front for instruments or line-level devices. Though there are four physical connectors, only two may be used simultaneously in a DAW. Using the front panel jack input(s) disables the XLR mic input.

You may notice that when recording with the 2i2 4th Gen, there are 4 input channels available in your DAW. Inputs 1-2 are used for the analogue inputs on the interface, while inputs 3-4 are used for Loopback.