You can't really tell but only have to believe your instincts, sometimes one can be wrong too and that's normal because failure is why we win sometimes, do your own research and have a positive mind, a quality project will surely appear to be one, the problems with bounty is payment evade by the teams
Every thing really needs research to the fullest, it is not enough just to rely on instinct, especially in terms of crypto, because there are so many projects including bounties that look interesting but they can still experience sudden scams even when we least expect it, this is a case that I have often encountered in crypto.