I was looking at NodeBB as an option for that sort of thing. The problem there is it’s not really structured for the kind of user-driven dynamic sub-community building that reddit and lemmy are built for.

But yes, that is essentially what I want, a traditional forum site with subreddits.

But then again, there’s also the design of the posts themselves, and how they’re shown on the user feed. Reddit clones put links and link access front and center, whereas there’s more clicks involved in even accessing post content on a forum.

Overall I still think it’d be easier to forumize lemmy, than to lemmyize NodeBB. The latter would require too many additions and modifications, whereas the former can be done hypothetically with deletions only, well, and a few switched defaults.