Hiya!
At this present moment there's no official way to play Chapter 2 outside of Patreon, since it's still in rapid development and being able to test the alpha as it evolves each month is more a perk of that specific tier than outright being a means to 'buy' it. Which I know is less than ideal and can understand the enthusiasm for wanting to play the game--but am not sure if there would be a good way to handle one time purchases for the alpha and wouldn't want to mislead people into what they were potentially buying while things are still so heavily in the works.