UWP, I guess. It's still similar enough from what I've seen, but I haven't used it yet. And WPF is still by far the best UI framework I've ever used.

Windows 10 only rules it out for me, also I think it might be tied to the Windows store although I'm not absolutely sure.

Absolutely not tied to the Store, you can distribute your appx packages any way you want and the users can install them with a double click. The only requirement is that the packages must be signed, so you have to buy a codesigning certificate or ask your users to install your self-signed certificate.

The app also doesn't have to be an UWP app: you can wrap bog-standard desktop applications (even Electron apps), HTML/JS apps (with direct access to UWP APIs) or even nothing: your manifest can just point to your live site, that can check if it's running in this context and then use UWP APIs, those are called "hosted web apps".