Thank you so much for sharing this. We're actively looking for alternatives to Postman right now, and would be heavily inclined toward an OSS solution.
I'm officially a Hurl user - really awesome work! Captures + asserts is exactly how I want to be thinking about API testing. Also, the VSCode extensions for syntax highlighting a .hurl file, and the "Hurl runner" so I can click a button to run a test, are pretty much all the GUI I need.