Thanks for the feedback.
I do agree that it seems that serial ports are a thing of the past for the NUC. The fact that they are not even visible from Win10 is indicative of that, i.e. the BIOS does not even enable them.
I would be nice to have an onboard serial to USB device (e.g. FTDI) as many other vendors do. This allows to keep a small form factor and have serial access from the CPU for low level debugging.