VPN (SonicWall) will not connect over T-mobile 5G Hotspot

T-Mobile using ipv6 instead of ipv4.

Keep in mind that, at least for me, the WatchGuard SSL VPN (based on OpenVPN) works just fine with the phone’s hot spot and I know the firewalls at the other end are not using IPv6 (I manage them…. :)).   

Find out for sure whether your VPN is SSL-based or IPSEC/IKEv2-based.   If the former, there may be something you can do, but if it's the latter, you may be out of luck.   

Both types of VPN work just fine when I use my regular ISP (Cox Cable).