I've read that it is possible to go back and complete Homestead Missions after you finish the game.
When I go to the Homestead, there are no Homestead mission indicators anywhere (Boston, New York, Frontier or the Homestead).
Even though Achilles is dead, he still appears in the house when I enter. There is the place on the wall where the painting should be.
I have even watched a YouTube video walkthrough of exactly where in New York to find the painting, gone there and no indicator to retrieve the painting.
Is it actually possible to do this particular mission after the end of the game?