I'm working on https://www.monsterwriter.app/
Every know and then I get an email with feedback or feature requests. Those are good opportunities to start a chat or a discussion with the user. Before I do that, I try to build what they want. Once Shipped, I write them a follow up email.
The other thing I tried is to reach out to people who I might think are interested in my product. I explained them that feedback is the most crucial think for me at the moment. This worked out quite ok. Some people took the time and had a look at the app and actually answered my question. I have to say that I only reached out to people who have the same mother tongue as me. In this case we already have something in common and it is more likely to receive an answer.