There's also MarkEdit[0], which is essentially "TextEdit for Markdown" and is definitely _not_ Electron-based:

> For perspective: at just 4 MB, MarkEdit is much smaller than Electron apps. Handling a 10 MB file with ease puts it ahead of TextKit-based editors. Performance-first editors built with Rust lack native features, while correctness alone rules out editors that rely on regex-based Markdown parsing.

[0]: https://github.com/MarkEdit-app/MarkEdit