I made this quick video to fully explain how to complete the Art Exhibition quest, since I was personally having troubles with it, and when I looked online I only found more confused people. Eventually I figured it out so this should solve any problems. Enjoy!
If you’re having any other troubles with Stranger Quests or anything RDR2, feel free to comment it down below and I may make a video about that too, or at least do my best to help out!