This repo contains the custom package_nekuneko_index.json file that can be used to add new third party boards to the Arduino v1.6.4+ IDE. Please copy this line and add it to your Arduino IDE preferences box:

https://nekuneko.github.io/arduino-board-index/package_nekuneko_index.json

https://github.com/arduino/Arduino/wiki/Unofficial-list-of-3rd-party-boards-support-urls

You can read an extended explanation here, this is just a resume. First install the following requirements:

sudo apt install python3 python3-pip python3-dev
python3 -m pip install gitpython click configparser

Optionally install python findimports module to check if there are missing dependencies:

python3 -m pip install findimports

You can check missing import dependencies by:

findimports bpt.py bpt_model.py

Install the missing dependencies if so and next check for updates by issuing this command.

python3 bpt.py check-updates

Finally perfom the update by issuing one of these commands.

python3 bpt.py update-index "NeKuNeKo SAMD Boards"
python3 bpt.py update-index "NeKuNeKo nRF52 Boards"

Commit the changes and you are done.

It could be necessary to add manually the propper submodules on the repo's root. In example, for SAMD:

sudo git submodule add https://github.com/adafruit/Adafruit_ZeroDMA libraries/Adafruit_ZeroDMA
sudo git submodule add https://github.com/adafruit/Adafruit_TinyUSB_Arduino libraries/Adafruit_TinyUSB_Arduino

In example, for nRF52:

sudo git submodule add https://github.com/adafruit/Adafruit_nRFCrypto libraries/Adafruit_nRFCrypto
sudo git submodule add https://github.com/adafruit/Adafruit_TinyUSB_Arduino libraries/Adafruit_TinyUSB_Arduino

Thanks to Adafruit, Ha Thatch, Tony DiCola and so many other maintainers to make this possible.