This feels like a really stupid question but I genuinely don't know. Gliders existed before powered airplanes, right? So people would probably could have made paper airplanes for fun prior to the Wright Brothers, but I have no idea and just had this as a weird shower thought and was curious about it now.
China did it apparently https://www.popularmechanics.com/flight/drones/a44112898/history-of-paper-airplanes/#:~:text=Chinese%20engineers%20are%20thought%20to,planes%20around%202%2C000%20years%20ago.