You can just clone and use offline.

Just open web/index.html file, it absolutely requires no server.

If you want a local server though, it is easy to setup: https://github.com/zakirullin/files.md/blob/main/docs/your-o...

Self-plug, I'm working on one, local, native, no web based ui, and minimalist. And it has no external dependency. The data is stored as simple text file, and the format is easily searchable with *nix tools.

Not going to be open source or free though, with 2 year perpetual license. I wonder how much that would interest you? My target is people who wants todo.txt like simplicity, but few useful bits. Only for Linux and Windows for now.

This is why I built https://www.asnotes.io - It's an extension for VS Code. I needed obsidian but usable on corporate networks that don't allow Obsidian or other pkms apps. It's designed to be version control friendly so no sync server is needed either (just use Git)

TiddlyWiki?

https://tiddlywiki.com/

Which has been around for 22 years now!

I recommend the helix text editor with the markdown-oxide LSP (and rumdl formatter if you feel fancy). All open source and even if you never update them they will work forever.