As you already know bounty sections[ the place where you will found many available campaigns who is providing bounties and airdrops. Apart from that, there are some websites who post information for upcoming campings for who'll going to distribute free coins. You can also go telegram, where lots of channels post about bounties. For example: you can join bounty detective airdrops channels for get more updates
the easiest in my opinion is to join a bounty manager channel account that is liked and often followed. I'm sure it will be better than going to forums and picking up lots of new and active projects.
I do that more often because I prefer a certain bounty manager to follow a project he's on rather than follow a project for which we don't know who's in charge of that project. maybe it's managed by their own team.