i have a headache, but after some long hours it finally works as expected. it was a combination of:
- multiple cold solders.
- usb hub chip partially burned (#ch334u), multiple times, in three different ways by inrush current.
- bad pin assingment.
- wonky setup with breadboards and jumper wires causing issues even with low speed usb2...

(all of that can be reduced to my incompetence, sure!)

lovely #kicad project by #adafruit helped a lot, as a point of reference. #diy #electronics.