Realistically, you could do as many as you want to. For TTRPG’s, as a GM I personally have a hard time when it goes beyond 4 or 5.
How few does it support?
At least yourself, and maybe friends. In more words, you could play it as a game by yourself as a Solo RPG, or, if you have friends to play with, you can play with them too, by appointing a GM (by suggestion, not necessity)
