9to5toys have a straight forward guide to turn you Raspberry Pi into an AirPlay receiver. Similar to the Raspotify project I previously installed on my Pi, this will work from applications other then Spotify like Overcast for example.
You shouldn't need to do much then run the following if your Pi is already setup.
sudo apt-get upgrade sudo apt-get install shairport-sync
Once installed test the install by running:
sudo systemctl enable shairport-sync sudo service shairport-sync start
Your Raspberry Pi should now be an option to AirPlay audio to, which again is a far better option then Bluetooth.