Philip Salmony has designed a STM32L4-based RF-to-USB dongle using a low-power NRF24 2.4GHz transceiver:
Overview of STM32, RF, and USB hardware design, schematic creation, and PCB layout and routing in KiCad using a real-world example project. (Timestamps in description) Various tips on controlled impedance routing, differential pairs, USB, and RF layout. Correction in schematic: NRF24 IREF pin needs to be pulled low to GND via a 10k resistor (not to 3V3 as shown in the video!). Fix has been pushed to GitHub.