Bookstack comes up a lot when “easy to use” is mentioned. It has a WYSYWIG editor by default and has a fairly simple install using a shell script on their docs website. Problems I have with it are it’s not really a wiki. You can’t link to nonexistent pages or see what other pages link to the current page. It’s more of a documentation system.

But I’ve seen it out in the wild being used for your use case (Tunic game wiki)