A fellow Qt/QML developer here (get-plume.come). Sounds interesting, what are you building?
Plume looks great! I'm curious how you implemented the markdown formatted text editing component - I need to implement something similar for the chat input.
I implemented the editor from scratch. The model is a C++ QAbstractListModel and the view is in QML. I'm writing a blog post about the implementation, it should pop up soon on my personal website (https://rubymamistvalove.com). But I can (and wish) to send you a draft soon, if you would like.