DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
Confluence - Confluence is content collaboration software that changes how modern teams work
Wiki.js - An open source, modern and powerful wiki app built on Node.js, Git, and Markdown.
TiddlyWiki - a non-linear personal web notebook
Nuclino - Nuclino works like a collective brain, helping teams bring all their knowledge, docs, and projects together in one place. It's a modern, simple, and blazingly fast way to collaborate.
BookStack - An open source knowledge management application that's focused on ease of use.