Hello
Has anyone successfully used a Heltec-M00 with chripstack V4?
Im looking at using this to connect my Milesight UC300 to chripstack UDP packet forwarder
Ive heard TTN do not allow the use of this because it only has 2 channels not 8?
Will this cause an issue with connecting to my UC300?
I took a quick look at it and it is indeed a dual-channel gateway:
The description also contains this note:
The node must modify the preamble length to communicate with the gateway!!!
So there you go 
You must modify your devices in order to make it work with this gateway. As well you need to modify the ChirpStack configuration to make it work with 2 channels.
If you want a low-cost LoRa gateway, why not buy / build a Rapsberry Pi based solution? Maybe you need to spend a little bit more, but you will save yourself a lot of time debugging why things don’t work as expected.