I'm looking to hang up some canvas art (already on stretcher bars). However, I don't know what kind of hardware I need to use, because I have no idea what kind of walls they are. They don't seem like drywall because they seem like they're solid walls. Here is a likely useless video of me tapping on the wall.
https://www.youtube.com/watch?v=ufvZzCUg1Gc
Is this plaster? If I want to put a screw in, should I drill a hole first? Should I be looking for studs?