There is another way which is be a bounty hunter to do Bounties campaign. You will get pay after do the bounty campaign tasks and you can trade the rewards into bitcoin.
bounty campaigns are not efficient way to make money because you dont have an assurance if a bounty that have you joined will pay you . the 3 ways that op stated on the first page are more better than applying and working on a bounty campaign but the only downside is that they mainly require a starting capital in order to get started with while bounty campaigns are free and you only need to invest your time . id better do faucets and other online jobs out there because they are more legit but again the pay rate is quit small .