Ask HN: Recommended Toolset to Build a Cross-Platform Desktop App in 2018?

And do any of these points affect your answer?

* Target platforms are OS X and Windows; easy adaptation to Ubuntu or other Linux flavors would be a nice bonus. Development will be mostly done on a Mac. Mobile versions are not planned.

* The app will have a GUI but minimal UI (at least at first) with only a few buttons and inputs. Later versions may build out more options and configuration.

* The core of the application involves text processing (especially parsing XML and JSON, and both parsing and writing CSS) and filesystem reads and writes. Future features will likely require HTTP.

* My experience is as a full-stack web developer. My strongest server-side language is Python; on the client side, I prefer React's philosophy to Angular's.

* I haven't decided whether to release the software under a proprietary license or to try to build an open source community around it (recognizing that those goals are not exclusive, but this is a sufficiently niche product that it's unlikely to support both).

* The target audience are consumers (especially computer "power users"), not businesses.

* Performance and scale are not and will never be critical. Data processing will be extremely minimal, file sizes will be measured in kilobytes, and the largest data sets would fit on a floppy disk with room to spare.

* The purpose of this project is to build the application, not to learn new and exciting tools (I'm not averse to that as a side effect, but productivity is the primary consideration).