The Fundraiser Stranger Mission in Red Dead Redemption 2 involves a woman who is collecting donations to expand the Quincy Harris Memorial Hall. The mission is pretty short and straightforward but provides another chance for you to decide how Arthur should be seen in the eyes of the people of Saint Denis.

Quest Initiation
The Fundraiser Stranger mission quest can be initiated at any time during the game from Chapter 2 onward. Please note that the mission will not be available during the Epilogue, so make sure to complete it before the end of Chapter 6.
The unnamed woman can be found in the northwestern part of the city of Saint Denis, to the north of the "N" in Saint on the map.
Part I
The mission only features a single part. Speaking to the unnamed woman in Saint Denis allows Arthur to learn about a fundraiser to expand the Quincy Harris Memorial Hall in the city. Arthur can donate $20 to the cause to complete the mission. Should he choose to do so, the outlaw will be rewarded with a small increase in his Honor rating.
The mission can also be completed by acting like a heartless outlaw. Instead of donating, Arthur can decide to loot the donation box. The act results in a loss of Honor points and becoming Wanted in the Saint Denis area.