I really like the concept of a federated message board. This is what I wanted for my life. However, Lemmy.ml is kinda difficult to surf through comments and it's actually bothering me. It actually clones the new reddit, while the old reddit was much better in terms of reading.
There's an excellent style available through userstyles that might make the experience more bearable. If you have some technical skill and time, you could make one that looks and behaves as old.reddit. I expect something like that will appear soon there as I hear more and more complaints about the UI.
I suspect this is the chance to make user experience the best. If they deprioritized refugees from reddit then the community would miss a huge growth opportunity. With growth comes more vibrant communities, more open source contributors, which is a feedback loop to make the site more appealing altogether.
I really like the look of LemmyBB. It's an alternative front-end for Lemmy that has the look of an "old internet" forum website. A few instances use it, but I haven't looked into it enough to know if it federates well.
It's not a Lemmy frontend, but an unrelated project similar to Kbin that also uses ActivityPub to federate. I am however not sure how well it federates with Lemmy right now. Probably needs some testing and bug-fixing.
The best thing about Lemmy is how it is completely separated from its UI. There are already different UIs available you can install to your instance or ask your admin to install. I think the LemmyBB might interest you: https://github.com/LemmyNet/lemmyBB