As a note, React / JS / web are not my day jobs, but I have enough experience, and this type of development makes sense to me.
I have been evaluating Flutter, but for whatever reason it is not clicking with me at all. I might have to go that route and bite the bullet, but I'm wondering if there's any other technology I'm overlooking?
App development: https://www.qt.io/product/qt-for-application-development/
I did a survey of what was out there for x-platform GUI toolkits (w/ Windows, Linux as primary targets and Android and MacOS as secondary) and most of them (tcl, gtk, ...) are unspeakably bad in terms of both developer and user experience.
The huge installer is annoyance but you get something that cares about font metrics, doesn't let you block the render thread, etc.