ETA: Ok, so it turns out that you can't launch Substance Painter from the Substance Launcher anymore. Great. Got it to launch from my Adobe options in my startup menu. Also couldn't update it, as normal. Had to fully install the current version first (which wouldn't open at all), and then select the new version. Of course, wouldn't you know it, my project is no longer right there, and I've got to go and find it. Along with all the custom materials I created.