How to build a wiki or any kind of database for our subs?

You should probably create an issue on the codeberg repo. I don't see an existing one on the topic when searching for "wiki".

I just use an external wiki/pastebin and put links to it on my community sidebar and one pinned post.

@PabloDiscobar you can try Hubzilla, it has some kind of wiki, but I still playing around as I am totaly new and exploring services in fediverse. My blatant copy paste with a bit Markdown work I done to show my fellow arknights players. https://hub.hubzilla.de/wiki/kotking/Arknights(28)20(29)resourses(28)20(29)wiki/Home