Qt looks nice but license fees are pretty expensive for small shops.
Could use the GPL version but I’m just afraid of becoming dependent on a tool that will keep the most interesting features only available for the commercial version.
Not at all! Qt comes with an LGPL version that you just must 1. link it dynamically and 2. If you change Qt's source code you need to publish the changes. (Not legal advice).
Most of what you'll need will be under the LGPL version. You can use the commercial version by paying and not publishing your source or via the GPL license and publish your full source code and everything else GPL requires.
I cannot recommend it more, give it a try it's easy to learn (I studied the basics in a day and a working prototype quite fast).
Something I've been working on: converting Markdown text into a Kanban view (in QML).[1]
Qt looks nice but license fees are pretty expensive for small shops.
Could use the GPL version but I’m just afraid of becoming dependent on a tool that will keep the most interesting features only available for the commercial version.