Just did the same exercise with a F072 discovery board. and ‘Voila’ that’s what I was looking for. It enumerates the first time I plug it in.
Not sure how that works with Win7, Does it need a special driver?
No problem though on Linux. I have now a new /dev/TTYACM0 device.
That broings uo the question: what is wrong with the L469 discovery board?