I have been looking at many forums and there are two I do like, Flarum and Talkyard.
The thing is that Flarum has some things that talkyard doesn't have and vice versa and I will give some ideas/suggestions and see if these things will come to Flarum or not.
First of all, Flarum is CLEAN and that is really nice. Minimalism to a point can be really beautiful if its made right, but there are things that could be removed/added to make this forum better.
Make the design more flat, more material design concept and remove the rounded edges on buttons and so on, and make it more square-like. Flat design is something that works well both in light and dark themes and flat is something that is trendy and will be for many years.
Add important things to the side of every thread (Read 1a below and see the picture)
Give us the option for threaded threads instead of flat threads. (same goes here, read 2b and picture )
It is very hard to find answers to your question in a thread when hundreds of people write and the subject gets divided and others ask questions in the same thread. Why do you think the biggest forums on this planet; Reddit, StackOverflow has threaded forums and not flat? Flat is not the future and will never be.
1a. In the FIRST picture, you can see the text; Topic, Category, Users, Replies and Activity shown. You get a lot of information before you even click on the thread.
This is what minimalism is all about, get most informtion with less clicks.
2b. In the SECOND picture you see a beautiful threaded thread. The arrows show who answered what and makes the whole thing much easier to read and understand. The Reply button is a square, material design concept and beside it we have heart, report and so on in flat design.
Why I still like Flarum more than Talkyard is just because of the CLEANINESS, but with these things to it and it will be much enjoyable to look at, search and quick get the answers we all searching for.