Logseq.com is “an open-source platform for knowledge sharing and management. It focuses on privacy, longevity, and user control.”
Logseq draws comparisons to Roam, one of many personal knowledge management tools that seem to be proliferating these days.
What I like about Logseq is that it works a lot like someone grafted a wiki onto something like Workflowy, but all of your data (which is ultimately just text files) gets hosted on your own GitHub repo (and soon, on local filesystem storage).
This YouTube video from Tech With Ed does a good job going over the basics of how Logseq works,