Tough request.

Instead of trying to control the conversation topic I'd control the conversation location. Make sure each topic has it's proper place, including a politics forum if you allow political discussion. Allowing a free-for-all in every sub-forum makes the sub-forums pointless.

Next go hang out in local facebook groups and pay attention to what interests people have. Adjust your sub-forums accordingly. Engage those people in their groups with subtle suggestions like "We just had a major discussion about this on example.com, this is what I learned".

Create the curiosity and the cats will follow.

Good luck.

I don't know your exact niche, but sounds like US targeted. I'm from Latin América but hang out on some english forums for topic interests and also to practice my writing skills. Over the years I've noticed in contrast to other english speaking groups, the US can be EASILY polarized, specially around politics and group identities, and every time a financial crisis hits, the forums become more polarized and bitter. Your area might not be this one specifically but pretty much applies, as you also have this kind of traffic and users, right?

In recent years I also noticed NON political forums to reduce their variety and, suddenly political topics appeared, that's not good. The web is not the same as in the past and not everyone is into forums, many moved to FB or Twitter and no it's not even remotely the same. I took my time reading some stuff on the web and yes I agree: most "discussion" areas, specially Twitter, are questionable in terms of mental health, as there is a lot of bitterness and aggressiveness, discussions are not discussions, it's mostly a wide set of personal attacks. I'm not even sure how worth it, it is to invest on forums nowadays.

Suggestions? get involved, really. I explored some forums from that perspective opening topics, interacting, and studying what people relate to (non politically) and it's been useful to understand what kind of content (articles) people are interested in, but mostly HOW. I'm one of those who openly talked about people getting dumber, lower reading skills, lower reading comprehension, needing more simple topics, mostly "one point at the time", it's not a pretty picture but even as others disagreed with me, over the years now agree this is happening. So, I have changed a bit my style of writing content.

In the past you could talk about topics in general, today it's mostly personal, not from the perspective of "this book is good, this topic is interesting", but rather like "let me tell you how this book changed MY life", it makes sense as now authors and content creators are relevant, consider youtube as an example. I've also noticed people engaging in quality of life topics, how to better their lives and status, success stories. Negativity is on the rise, it's a trend, and there is a lot of depression, lots of it... so it's not an easy task to keep readers engaged.

Any suggestions on positive methods to encourage local topics?

Asking people in diff ways how something changed their lives works, like books, films, songs, places, events, traveling, etc. My 2 cents.

Blog style? I didn't remember this when I posted above.

Someone on a local forum (with lower traffic every year) asked questions about traveling. As many of us visited those regions, we shared and it was interesting. The best thing is, this guy did went there and posted how a nice time he was having and then added "I think I will try to post every day things as I explore the area", and it's been interesting.

Someone else who was a former athlete posted his progress getting back to shape.

It seems to have become a trend in recent years where people can't help discussing politics.
My top suggestion is to clarify it with that members that it's one of those topics you don't discuss, in the same way that religion is also a no-go area.

Invite your best participants to get more involved topics. Of course, those participants need to understand that you don't do politics. Ask them what topics they want to talk about. See if there are opportunities for them to start those discussions. Look at the current news topics on the subject, both locally and nationally, and see if there are topics related to your sector. Most people that are engaged will participate.

Expending time and effort into moderation will be essential regardless of control/intent of topics is required. Be prepared to invest that time (and possible expense) to accomplish that goal.

Meanwhile, craft a TOS that clearly states what is acceptable content and make sure ALL VERIFY they have at least been SHOWN the TOS to continue.

Several years ago I began to segregate popular topics, giving Sports, Tech, and Entertainment their own sections so that the locally-focused boards could talk about local topics.

Everyone hated it! People quickly stopped talking on any of those new forums because they didn't feel like they got as much attention. So all I really accomplished was squashing those discussions entirely :-(

So now I'm hesitant to do the same thing with politics. I recognize that the discussions are running people off, but eliminating them would squash the majority of my posts! I hate to cut off my nose to spite my face, if ya get the reference.

I've tried to create my own topics to stimulate happier discussion, and it does help, but I'm just one man with limited time and imagination :-/ I'm trying to find ways to encourage 50 people to do the same thing, so it's not all driven by one person.

Luckily / unluckily, Facebook is virtually dead in my area :-) That's good for me business-wise, but bad in the sense that I can't use it to find topic ideas. The local newspapers only print weekly so I use that for ideas, but there are usually only 1 or 2 topics worth discussing. That's why I'm thinking more about message board games, etc.

So now I'm hesitant to do the same thing with politics. I recognize that the discussions are running people off, but eliminating them would squash the majority of my posts!

Letting politics run wild is a no sum solution. Allowing politics to run rampant will finish all "conversation"---whatever value the discussion board might have had is rendered moot.

That will result in zero sum...

Hard choice!

Meant to add:

On forums and email listservs operated over the last 30 years, four topics became verbotten:

Politics
Religion
American Civil War
Creationism/Evolution

Remove those and it is a wonder how much fun and entertaining the conversation(s) can be!

YMMV

(Note: only works if you MODERATE and REMOVE bad actors regarding policy)

My suggestions on this post might sound aggressive or radical, but at the end of the day is also about embracing your power (as owner/founder/admin) in your hands, and also about facing people, confronting them. Might not be the ideal solution, but perhaps the more assertive to avoid feeling like you have no control over your property. But first, the topic begs the question of policies and guidelines, every forum or website must have one, where you explain what's allowed and what's not allowed, people must agree in order to participate. If there is such thing, then easy: you, you and you OUT! for disrespecting the limits and rules. If there is no such thing, then add it, and make it clear for everyone that those policies will be applied because otherwise they are killing the forum.

Several years ago I began to segregate popular topics, giving Sports, Tech, and Entertainment their own sections so that the locally-focused boards could talk about local topics.

Everyone hated it! People quickly stopped talking on any of those new forums because they didn't feel like they got as much attention. So all I really accomplished was squashing those discussions entirely :-(

So now I'm hesitant to do the same thing with politics.

Example #1 What if you take the mental health route?, see, in my family when I lived there (younger), a few older ones got caught in the NEWS discussion, useless topics about prices, inflation and negative news. Obviously this wasn't right and I got intoxicated, I tried (as you explain) to promote new interesting topics, videos of concerts, documentaries, films, etc and it didn't really work because people after all, kind of feel alive, important, smart, or involved when discussing those intoxicating topics. So, I ended interrupting and confronting people, my best solution was doing it right away when they started talking about the same things and I would say "ok, let me interrupt you, is this about politics again? negative news? 3, 4, 5 topics? and all of them are NEGATIVE?", ok, then let's try this, can you... tell me something positive today? anything? and they struggled, and eventually noticed everything coming out of their mouths was negative.

Example #2, on a forum I participate since 2007, people got caught up in inflation and politics discussions, I got bored so I asked them directly why they were such XXXXX [negative term saying they were weak, useless and even not masculine] oh they got mad!, but I added they were not behaving like real men with brains and solutions, because all the posts were about complaining. Yeah they hated it but the message was received and so they stopped, a moderator said this sucks but hey you are right, a man has to deal with it, complain on, but at the end of the day lust do something.

Example #3, on a forum where depression took over, I confronted them on why they bragged about success and being smart on some posts, but complained like cry babies all over the forum as useless individuals, you better shot yourself (I didn't say it like this but it's the short version), they got offended, I got a point, and what I did have some real effect. And for a while I hinted things like "let's talk about computers, and let's wait who will be the first loser to come crying about oh I hate the world it's not a sunny day", oh yes, it worked.

Example #3, explore posting the effects of negative news and politic discussions, there is literature about it, things like 5 minutes discussing politics and what you could to do improve your life in 5 minutes. I worked on a media company owning newspapers, tv, magazines, etc and they loved these topics because people fighting means people engaged, researching I found research and articles on the web (serious ones) about the negative effects of newspapers on people. When I read it I said "oh this is familiar", and turns out I discovered articles talking about WHY certain newspapers (Canada was one of those countries, and also England I think) where their website shows diff content than the printed version, and they also have 2 online versions, one for outsiders in the world, and another one for local people, because they noticed the negative impact on them, this reduced investment, economic activities, business, social quality, etc. I'm serious about this. This was around 2013-2015 when I found it and I remember saying something about it here on this forum. This 2022 there was a related discussion so I wanted to share those articles, sadly I didn't found any, yes I took my time and it's just not there online anymore, I should have saved the content for later, I didn't.

Example #4, on another forum there are some who brag about being successful millionaires and they have their own followers there, sure, ANYONE can say anything on a forum and copy paste quotes or articles about finances, specially if you take the quest of telling people "oh you are doing it wrong". I'm not 10, so yes all of them sound like 15 year old kids with no life, so at one point I challenged them saying how silly it is to have "successful millionaires... on a dying forum... discussing negative topics... and proving they have nothing better to do with their lives and instead sound like complete failures", guess what? message received!

Even if people eventually stop talking, a dead forum is better than one wasting your time with any kind of ROI. Positive efforts are good, but you are the boss, and people often hate feeling they are being "educated" around certain topics, so they take offense and leave, instead challenge their views of success, how they don't sound successful at all.

A popular forum where I'm a member banned all discussion of politics, and enforces it. It really seems like there was no other solution.