I think you can just set the I2C pins in MyBoardNRF5.h without remapping the pins in MyBoardNRF5.cpp.
Look in MyBoardNRF5.h, under the Wire Interfaces section. Set SDL and SCA to 30 and 31 as appropriate for your board.
This should work with Domoticz, it's what I intend to use with it. I've received the boards from China and I'm currently working on a version 2 of this board. There are some errors in the design of version 1 that I need to get out. New version will be up shortly.
I finally received the boards from the manufacturer(big thanks to @Seeed-Fusion). I manage to assemble one board by soldering the components and such and...it WORKS(including OTA)! I will post the instructions on openhardware.io project page.