Does anyone have a Chateau 5G working on T-Mobile in the US? I have a business SIM for Fixed Wireless access.
I am using Fast.t-mobile.com for the APN. The router will not get an IPV4 address. It does get an IPV6 address, but since T-Mobile does not do prefix delegation I can’t get IP addresses for connected PCs via SLAAC
To add additional information:
I have IPV6 working. I use this APN - Fast.t-mobile.com and I’m able to get an IPV6 address. I don’t get an IPV4 address. A laptop connected directly to the router works on IPV6. Since I only get a /64 PD from T-Mobile I am limited to using devices directly connected to the Chateau 5G. The rest of my devices that are behind an RB4011 can’t get an IPV6 address due to the PD of a /64. 
I had a similar issue on EE in the United Kingdom, I had to change the APN type from auto to ipv4 to get internet access on my business sim.
I tried that and I get a login failed message.
In working with T-Mobile business support I’ve found out that since this device is connecting to T-Mobile’s 5G SA network which is currently a pure IPV6 network there is no way to get an IPV4 address. I haven’t figured out how to force the Quectel RG502Q-EA modem to connect to LTE and 5G NSA networks. I found the AT+ commands to disable the SA mode, but as soon at I enable the lte interface it seems to override the command that I issued to disable 5G SA.
I have similar situations. I find out if I force my modem to LTE I will get IPv4. One thing is interesting, when I am on 5G SA, I do get ipv6 PD to my network. My laptop has no problem accessing Internet, including IPv4 only sites. But my router can’t access any sit( when I ask it to check for ROS updates, it says no Internet)