I'm the developer of Daino Notes (also wrote in Qt C++ and QML). I wrote a blog post about the development here: https://rubymamistvalove.com/block-editor. I wrote about many challenges that I guess you also faced as well (for example, getting the underline markdown from cursor position in the render text. It's nice to see more Qt apps try to achieve the same.
It's a shame how scrolling feels in QML, ah? I tried to play around with QT_QUICK_FLICKABLE_WHEEL_DECELERATION but still it's not optimal. At least on Linux on Windows it's a problem, on macOS a bit less so.
Hey there! My note-taking app works on Linux, welcome to check it out: get-notes.com
Currently, there's no sync or mobile app, but that's in the works.