There is a shellscript which downloads/builds a complete arm-none-eabi cross-compiler toolchain in: tchain.sh

the results will be installed in 'arm/', so you can set your '$PATH' to <pathto>/toolchain/arm/bin/arm-none-eabi/

in case you have a blackmagic jtag debugger (highly recommended) you can use pyrsp to make your debug sessions more fluid.

You can use use the sub-module in NRF-BTLE-Decoder.

if you have some gnuradio compatible SDR that can tune to 2.4GHz then you can use nrf2stdout.py to feed the nrf24-btle-decoder like this:

$ nrf2stdout.py | ./bin/nrf24-btle-decoder -d 1

you can play with nrf2stdout.grc in the gnuradio-companion if you need finetuning.

happy sniffing!