@mherrmann has written a book on using Python with QT for cross-platform GUIs:
Something worth considering for those contemplating creating a cross-platform app.
@mhermann - if you are listening, care to share the experience of writing the book, using Payhip, and promoting via video?
Thank you Steve! I appreciate the share 
I just put the book online yesterday evening and just made my first sale. Maybe it even came from your link 
The motivation for me to write the book is explained in the video - I felt the existing ones simply weren’t very good. I wrote the book with LaTeX and reused / adapted some contents I already had written elsewhere. I’ve spent 155 hours on this project so far, including market research, content planning, writing the book, creating the video and creating the sales page.
I only just started to use PayHip. I like that it handles EU VAT for me, and pays directly into my Stripe / PayPal accounts. I was inspired to do a video after seeing @mijustin 's https://devmarketing.xyz/. I still want to improve the video, by showing screenshots etc. But I couldn’t wait to put it online. PayHip also has a very pretty interface in my opinion. I’ve also used Gumroad before, but it often feels buggy. And it only supports USD as the main currency, which is not ideal for me, being based in Austria (and thus preferring EUR).
What’s the licensing situation with QT? Commercial license is very expensive ($5k per developer), and I’m not sure based on quick look at their site what you can do with open source version. Can you use it in commercial projects?
Good to hear of PayHipp and their VAT service. Thanks. Please keep us updated on your experience with them.
No problem Just ping me here in a few months and I’ll be happy to report.