double nat on console home internet

Unfortunately, the fix is not just something as simple as a firmware update to their modem/router.

The core problem lies in their network topology on the other side of the modems.  Basically, an infrastructure design issue that needs to be reworked first.  They have large banks of v4 addresses, but for whatever reasons they will not assign those to us on a 1-1 basis like they do with the likes of Spectrum or ATT... instead they are used more like a VPN, potentially sharing one address with multiple clients (like a CGNAT setup).

As mentioned earlier: XLAT464. This is what they implemented to deal with mixed IPv4/v6 through the IPv6 portions of their network.  As mentioned in the RFC on this like a decade ago, this core design breaks unsolicited inbound traffic that would require port forwarding to work.

There are some potential work arounds they could put in place, but it would require considerable resources and partial redesign of their networking strategies to make it work how we would need it.

Some have mitigated issues with their own VPN's, but YMMV... it would need to properly support P2P traffic, and in the case of game consoles would need to be running on a router as well.