As a start, I am an owner of an STM32F469I-Discovery board. When I tried out the USB Host applications that came with STM32CubeF4, whether it was "HID_RTOS" or "HID_Standalone", I could not input a single thing with my USB wired keyboards even though they were all enumerated successfully and I tried 3 different keyboards.
On the other hand, the USB mouse I had with me worked as intended by the examples provided. While I will admit that all 3 of the keyboards I tried are not your typical brand stuff (e.g. Logitech, Microsoft etc.) but some generic Chinese devices, they all work perfectly fine on Windows/Linux machines which leads to me to believe that it is very likely a software problem. As a matter of fact, I tried the same examples from STM32CubeF4 v1.10.00 and v1.11.00 and they both produced the same results which is not surprising since they are no changes as far as I could tell.
However, I cannot fully dismiss that it is not a hardware problem either. Therefore I would like to request all STM32F4xx users who have had success with using a USB keyboard in the examples which were mentioned above to provide more details about the keyboard you used.
If it is indeed a software problem, then perhaps ST may want to have a look at it. If it helps at all, I am posting the PID and VID of the USB wired keyboards I had used for my testing below.
Keyboard No. 1 - PID: 260h | VID: 9dah
Keyboard No. 2 - PID: 1503h |VID: 1241h
Keyboard No. 3 - PID: b23h | VID: 1a2ch