@no1warr1or Thanks for your research into this! I also bought this device to use with my AT&T 5G service, spent about a week trying a thousand combinations to get it work work, detailed here. Please let me know if you have anything else to try before I buy a MoFi or something…
FWIW, in no circumstances should anyone ever purchase or use a Netgear M6, the 3 I tried were the worst devices I’ve ever used in at least 5 different ways. That being said I have one for sale… 
Super disappointing, was so pumped on the Spitz.