For the STM32F042 project I found a third party USB library that does not depend on Cube. It is a bit sad that it supports only CDC and HID classes. Well I hope either libusb or libhidapi can access them properly under Linux, but so far I am working only under macOS.
Now I need a USB VID/PID pair. There is an interesting list on USB-IF website called
obsolete USB VID's. I wonder if you would consider it safe for tinkers to just grab a VID from the list, pick the preferred PID, check on an some databases to see if the VID/PID pair is used anywhere, and if not used, go ahead and bake it into the prototype?
Speaking of, it seem to me that the VID 0x0002 from Ingram was never used for some reason...