The experience with bounties from HRF wasn't great. No one has answered to the calls for implementing what they wanted because the work was too much and the risk of not getting paid very real. The experience with grants in general from Spiral is also not great: many random developers making cool but useless projects, wasted money.
The two kinds of open-source financial support that have worked so far are:
- Paying people who are already doing useful work so they can continue doing that. That is the experience of some people who are "maintaining" Bitcoin Core, for example, or other open-source projects. You're doing a thing, you've proven yourself valuable and you definitely seem to be interested in that personally such that you don't need a boss telling you what to do, so take the money and just keep doing that.
- Structured open-source initiatives, like the LDK effort. Although LDK is arguably useless, it has a stated goal and that goal is being delivered. I don't have any knowledge about how its development process works, but they have people being paid and "bosses" that direct the work to be done, as any team needs. So it is not the same as an open grant.
The thing that is missing is a way to provide these open loose grants to people that don't require bosses, but also that don't just pick a winner and let them do whatever stupid idea they might have (Spiral grants), and also do not mandate that they do something big before being paid and offers no guarantee of that they will be paid whatsoever.
The solution: smaller flexible bounties in large quantities
My suggestions is: instead of giving 1 bitcoin for a huge very specific project, state some "principles", or "problems", in a loose manner, that you want to see solved. For example, "we, the organization X, wants to see projects that use zero-knowledge proofs to help Bitcoin somehow, because we love zero-knowledge proofs".
Then state that you're going to give 20 grants of 0.05 bitcoins each, at random times, for projects that you see being done that may be on the right track.
That will tilt people that may had a small inclination to work on these problems to actually start doing something, and if they see that what they're doing is being appreciated and awarded with a payment, they will be more incentivized to finish it. There could even be a conditional bounty (like HRF did with Cashu) for finishing the project with certain requirements, but this only works after some structure is already in place for a certain project.