I am currently using the Bookstack wiki of the umbrella project for general instance specific documentation. However it does not lend itself well for providing community specific wikis.

Dokuwiki could be used for that more easily, but I would need to write custom SQL queries to link the accounts to the Lemmy database. This is a bit annoying to do but unless you have access to your own Lemmy database to test this, it is not really something I can get help with.

However right now I also don't really see the need for a complex wiki. Basic community details fit in the side-bar text where they are also federated to other instances.