My first thought is reduce the complexity for now and start a Lemmy community for what you want. I know it's not going to be as versatile as a full-blown forum and any specific requirements you have might not be met, but there are creative ways to manage this as a moderator with the API.
It would be free, you wouldn't need to worry about the web security aspect for now and it might let you feel out how to manage topics/projects before you build an actual forum.
Sorry I couldn't directly answer your question, but was hoping that an alternative approach might be of use. It's just that hosting and managing a forum can be a time suck.