For just rendering (no editing) you could use https://github.com/litehtml/litehtml (C) or https://github.com/DioxusLabs/blitz (Rust).

Both are actually lightweight HTML rendering libraries, so you need to compile markdown to HTML to use them. But there are many libraries for that.

The link says litehtml is C++. I can't tell if it exposes an FFI (I bet not)

Of course blitz doesn't expose a FFI either and also if you need anything interactive you have to use the dioxius framework or implement you own APIs for that as well as take care of animation yourself.

Does it mix well with text input? What I really want is a native WYSIWYG Markdown editor - in a similar fashion to Typora (Electron) or Milkdown (a JS library).