If you don't want to join on bounties then you can join on campaign with bitcoin payment.
It is rare to find a bounty that pays in bitcoin. Do not confuse Signature campaigns paying in bitcoin with bounty campaigns. The closet I got was that some campaigns paid in Ethereum and not tokens. But most of them will pay in tokens. This is justified because they want their project to be known and what that liquidation of their token.
Also the project may not be successful at which point the tokens will be valueless approximately but bitcoin wont - thus paying hunters in bitcoin means a waste of funds for them. This is effectively a method to blanket scam these people or at least something that I have felt unethical from the point of view of bounty hunters since my first days here.
In the recent days no bounties were paying any rewards to the participants due to project failure or it might e a scam project so we can join on legit project if they have bitcoin paying bounties it might failure but our effrots will get worth it.