My dad bought a USB turntable which worked great with Audacity. I'm not sure which model or brand it is, but there are lots available. He didn't bother splitting the tracks as he is happy to just listen to whole albums, but that would probably be fairly easy to automate if you had a lot to do. Will that audio interface you have keep the two inputs as separate channels? Seems more likely it would mix them into one mono channel (on my similar interface the left and right outputs are the same unless you have a stereo signal coming from USB).