As I write this, the latest version of CircuitPython is 2.2.4.

Install CircuitPython

• copy adafruit-circuitpython-feather_m0_rfm69-2.2.4.bin to my local drive.
• Double click on the Feather's reset button to put the Feather into bootloader mode.
• Use BOSSA to install Circuit Python onto the Feather (choosing the option to erase all files).
• Click the reset button on the Feather to switch the Feather from bootloader to running mode.
• Minimize the amount of space taken by files. From a Terminal window:

mdutil -i off /Volumes/CIRCUITPY
cd /Volumes/CIRCUITPY
rm -rf .{,_.}{fseventsd,Spotlight-V*,Trashes}
mkdir .fseventsd
touch .fseventsd/no_log .metadata_never_index .Trashes

Install the RFM69 library files

• Make a lib directory on the CircuitPython, e.g.: mkdir /Volumes/CIRCUITPY/lib
• Copy the files into the CircuitPython's lib directory, e.g....assuming the contents of adafruit_bus_device and adafruit_rfm69.mpy are located within the directory the terminal window was open to: cp -r . /Volumes/CIRCUITPY/lib/

Test

The test is between the Raspberry Pi and the Feather. The Raspbery Pi's code is located....