Long story short, my laptop crapped out on me (it wouldn't boot into Mint 20), and my brother managed to fix it. The sound worked fine after I got it back from him, but then stopped working one day and hasn't worked since. I've tried upgrading to 20.02 to see if that would resolve it, but it didn't work. I checked my driver manager (thinking it was a driver issue), but all of my drivers are up to date. Because this is a Lenovo Thinkpad X200 Tablet (which was made around 2008 from what I looked up), it's old, so maybe it's a hardware issue brought on by old age.