I will advise you to stay away from bounties as most of them never pay and those that paid at last reward you with worthless coins, looking for signature that pay you in stable coins may be difficult to find but keep an eye in the bitcoin market place. bitcoin paying signature campaigns announced there from time to time.
It's not true that a bounty campaign will never let you earn. Having participated in them in the past, I have earned quite well on several occasions. It mainly depends on researching the project very well before joinin campaign. In the next stage, you have to calculate well whether the campaign will pay off even with a large number of participants. After that, it remains only to be lucky for the project to succeed.