brent Honestly, forums are great IF, and I mean a big IF you have a good community and enough people there. In the modern era of social media, more of the younger generations will go to where they can get answers for many different things at once. They can have 1 account and access dozens of focused groups. I used to run a local PC gaming tournament (early 00s), and we had a great forum with tons of traffic. If I were to do that now, I would likely have to do it through Discord, Reddit, etc., to get any traction.
Most of the projects I have worked with that had/have a forum have continued to see a decline in forum participation and a growth in social media-type channels, like Reddit and Discord.
It is what has surprised me with Solus and honestly one of the things that drew me to the community here. While this forum is not a gamer forum or something where you get 100s if not 1000s of posts a day. It has a constant amount of posts, and it is engaging.
The problem with Matrix and Mastadon is that there is more barrier to entry than other social tools and just not as easy for people to get into. I love and use both, but I get why many out there don't.