Hedgedoc is fantastic. If you’re okay with your notes app being web-only (without an app or even a PWA) and you don’t need canvas notes or multi-note queries, you should check it out.

First, every note is Markdown, but it supports a ton of things natively. It has native Vim, Emacs, and Sublime (the default) editors and it’s built to be great for collaboration (if you want).

It also has

• syntax highlighting for a ton of languages
• Mermaid.js support
• LaTeX support
• easy drag and drop image uploads
• a solid mobile interface (for a webapp in your browser, at least)
• built in revision history
• support for other diagram tools, like graphviz, flowchart.js
• a bunch of other little Markdown enhancements that make using it feel oddly intuitive

And best of all, they have a Hedgehog for the icon! (I may be biased.)