From when I last tried it, Outline lacks any of the database/datatable functionality of Notion, but Appflowy seems to already have much of this functionality built in (or at least something like it is visible in one of the screenshots shown). Furthermore, logins in both the self-hosted and cloud versions of Outline require logging in with third party providers, no local accounts, so it can never be fully self-hosted.
Are any of these options a git repo under the hood for the actual knowledge base?
It’s very valuable to be able to have the double workflow of a nice web interface alongside a plain text developer git workflow and leads to a very future proof knowledge base.
There are quite a few options for markdown + git knowledge bases, eg. Obsidian. You can easily find more alternatives discussed here on HN by starting a search on Obsidian.
If you’re looking for more of a CMS there’s quite a few options out there, most notably static site generators like docusaurus or vuepress. Plug: I’ve built a small tool to generate the markdown from notion, which allows me to use notion as my CMS editor while keeping the generated site fully under my control. https://github.com/meshcloud/notion-markdown-cms