The best option is to just support the developer/project by the method they prefer the most (ko-fi/patreon/crypto/beer/t-shirts etc).
If the project doesn’t accept any donations but accepts code contributions instead (or you want to develop something that doesn’t exist), you can directly hire a freelancer to work on what you want, from sites like freelancer.com.
Are there better open source bounty sites/systems?
The best option is to just support the developer/project by the method they prefer the most (ko-fi/patreon/crypto/beer/t-shirts etc).
If the project doesn’t accept any donations but accepts code contributions instead (or you want to develop something that doesn’t exist), you can directly hire a freelancer to work on what you want, from sites like freelancer.com.
Some options are listed here https://www.oss.fund/categories/bounties/