Hello,
IP passthrough is turned on by default on InvisaGig, and this works very well for our customers.
The IP address and DDNS usage is being mis-defined in usage for many. DDNS does not work behind CGNAT, regardless of what any youtuber may say.
The IP address that gets relayed is a private IP, thus not accessible by any service.
If you apply for a static public IP from your cell carrier, applied to your account/SIM, then this is totally different and makes DDNS non useful as well since the IP is static and publicly addressable.
You can fix this with either a local VPN service (VPS) that you have a public static IP assignment for and route only your DirectTV traffic over the VPN, or get a public static IP assignment from your carrier.
There are other more complex ways with more feature controls and fun stuff, like our article here: How to Get a Public IP for Open NAT, Plex, etc. Using pfSense & WireGuard … but again, using a VPN service.