Hello there,
I just bought one for the quite large input voltage range and I am really disappointed by the lack of documentation for this board. Moreover, examples provided using BLE functions are very poor and not detailed at all. It may explain why we cannot find a lot of application examples with this board.
In comparison, Arduino_BLE library looks much more interesting but I did not succeed to use it as board does not seem to be compatible.
In my case, I would like to use it quite basically by monitoring a few measurements using nRF connect app on my phone. Something very similar than usecase presented in this Article
… but it does seem more complicated than I thought 
If someone had some clue to deal with this board, I would appreciate to learn your experience!
Regards,