Adobe flash is going to be stopped in updates and so on, This does not mean you will not be able to play graal on PC after 2020. Flash is only going to be stopped in being redistributed and updated. This won't stop you from playing graal on flash if you already have it. Even if Google stops enabling support you can always just use an older version of chrome. Plus graal just make a steam version of classic if for some reason they cant make graal work on the website anymore(Which i would be happy for anyway).