Obsidian.md - A second brain, for you, forever. Obsidian is a powerful knowledge base that works on top of a local folder of plain text Markdown files.
HowHive - Knowledgebases for teams and companies of all sizes. Knowledge sharing and finding made simple.
TiddlyRoam - An open source non-hierarchical notebook.
Raneto - Open source, flat-file Knowledgebase platform that uses static Markdown files
Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
openKB - openKB is a Markdown Knowledge base application (FAQ) built with Nodejs and ExpressJS.