Your OP seems to suggests you have an implicit expectation that this is easy. It is not.
don’t expect fast growth initially
I have one forum that’s been around since 2012 that is very niche. It gets 15 sign-ups and about the same number of new Topics a month. But it continues to live on. Would I shut it down because it only plods along? No way. It is a valuable resource for those interested in the subject.
Be patient and accept that some places move and grow slowly.
chat is double edged
Use of Chat is contentious, what people commit to chat they won’t write to a quality Posts. And Posts are what attracts people to your site via SEO.
Chat also relies on people being in a closer timezone. Topics are more friendly in that respect.
As per Hawk write leading Topics on subjects that people are interested in. That will eventually show up in search results and get views and drive engagement.
Also multiplatform attack:
A friend of mine, starting from nothing, began a broad presence on twitch, YouTube and discord.
He now has about 2.5k Twitch followers and 1k on his Discord (though tbh Discord users tend to be a bit less loyal). He’s almost a year in.
His growth to begin with was pretty fast but it has slowed.
I think from this you can draw that having a broad presence on social media is one key to getting off the ground.
reduce friction
Make is easy for people to sign up and support all the major social logins, ie at least Facebook, Google and Discord.
don’t give up
Finally, just keep going for a bit and don’t give up. Care less about growth even and just write about what interests you and see what happens after a much longer spell.