nRF24LU1+ (and derivatives') packet demodulator GRC (v3.7.11) diagram for Ettus USRP SDRs. Based on the one for HackRF.
Captured packets are pushed into a FIFO under /tmp/fifo which then can be used with omrilluz's nRF24 decoder (https://github.com/omriiluz/NRF24-BTLE-Decoder) like:
cat /tmp/fifo | ./nrf24-btle-decoder
Tested with USRP B200.