A list of the 4 libraries in the architecture nrf52.

Arduino Low Power Power save primitives features for SAMD and nRF52 32bit boards
Codec2 The Codec2 library is a proof-of-concept for running the Codec2 audio codec on an Arduino-compatible Adafruit Feather nRF52 Bluefruit LE board.
LoRa Node LoRa Node library for Arduino LoRa Node Shield.
Servo Allows Arduino/Genuino boards to control a variety of servo motors.