Ahh I see, I figured that that issue was related to the TTIG specifically connecting to TTNv3, I didn’t realise it was also the case when I’m running my own Things Stack locally.
For others with a similar issue, here’s an explanation of it:
However, I did see some others who are using the Multitech Conduit, who do have issues but have managed to get CUPS working correctly? (though they are using a different version of the gateway):