, though it's a slight change in the topic relating to this, what about boards which are inactive or have little activity?
I think the Lua board is a good example, since it only seems to get about one or two posts every 1-2 months and a lot of threads there are still unanswered; many people who post there also never seem to return. I have experience with Lua and I could post there if I wished, but there is no point if nobody else engages with it. It's also a language intended to be embedded with C/C++ code and doesn't hold up as well in my opinion as a standalone language. So if you didn't wish to remove it, maybe consider moving it under one of the C boards?
On the topic of the C boards, maybe restructure them so that it's all under one roof rather than have a separate board for C, C++, and C#? They are all part of the C family of languages, they just greatly differ from each other. So, perhaps have it: C family board -> general C programming threads and links to specific C language boards(one for C, one for C++, one for C#). Just an idea.
Another good example of an unused board is the Godot board in game development: the only thread there was posted in 2019! The last post in the Unreal Engine board was 2020! I think if you wish to keep these boards around, you would need to encourage people who use these tools to post there or find other ways of attracting newcomers to those boards specifically(perhaps some kind of 'Board of the Day' system? I'm not sure if there's an add-on for such a thing or if you'd need to implement it yourself).
It might be wise to consider another board restructure as the site is nearly at 4500 members and will very soon approach 5000+ members. Then of course there is the problem of retaining activity on these boards, but that's for another day.