Comment by codingdave

This is the same answer as growing a for-profit product. You need to stop spraying random marketing attempts, and look deeper at who uses it today, and why. What problem does it solve for them? Who else has that problem, and where does that audience actually spend time - both IRL and online. Then you craft a message that clearly and concisely show them that you understand their problem and have a solution available, and you share that message in the specific locations that your specific audience knows and trusts.