Great project! Is there any mechanism implemented to ensure compliance with the EU regional limitations of the maximum duty cycle in the 868-870 MHz bands? ZigBee can be quite chatty as it operates on the unrestricted 2.4 GHz bands.
FYI there is also a 2.4GHz version of Lora. It has very high sensitivity modes close to the performance of the sub-GHz version, but also has high performance modes that give you up to 2Mbps.
What gp asks for is that regulation requires either polite transmissions aka listen before talk aka clear channel assessment, ie before we send, listen for a while and back off if channel is busy. If LBT isn't used, there's a maximum allowed transmission duty cycle stated.
Zigbee typically uses LBT, Lora doesn't. Hence, a clear zigbee channel may result in a very chatty lora channel.
And another problem is the difference in bandwidth, where zb uses 250kbit/s at 2.4 GHz and a transmission may take on the order of a millisecond, Lora even on minimum spread takes hundreds of ms, on max spread a single transmission can take several seconds.
This limits the scalability of lora networks in dense physical deployments. Lora primary use case is the once-a-day-ish sensor transmission.