Hi Scott,
I wrote custom firmware, based on STM32CubeWL Firmware Package. I’ve also designed my own PCB width Lora-E5 module. It is mostly a breakout board for the module, just connectors and antenna matching.
I know only so much about certification, you have to ask authorities in your country if you have to certify or not. The way I see it that hardware is certified, not the software. So, any change to HARDWARE requires certification if you want to sell it to end customers. There are some exemptions, but you have to verify with people more knowledgeable in this matter than me. Point being that software is not that much relevant. Otherwise you have to go through certification each time you release new firmware, also bugfixes. Doesn’t make sense to me. Again, this is not an advice, just my own opinion.
Experience so far with the device: 97% of the batteries, voltage is above 3.1V on 2 fresh AAA batteries, device is outside of the building (low temperatures). I have to say that from power consumption point of view this is the best device I’ve built so far. TI-based ZigBee devices (cc2652rb) draining batteries faster.