Yes, I've confirmed that IPV6 works perfectly fine while IPV4 doesn't after I disabled the "Interface Status Tracker" under "Multi-Lan". Did some research and it seems like Tmobiles is fully on IPV6 and using 464xlat to translate IPv4 packages to IPv6 at its Gateway (explains why my wireguard VPN on ipv4 is flaky recently). There is no issues with simcard or network registration as I confirmed with AT commands (e.g AT+CEER, AT+COPS?, etc)
I tried to install 464xlat package on the GL-XE3000, and I was able to ping ipv4 IP like 8.8.8.8, but noticed it was flaky where maybe 1/2 of the ping failed. Also I noticed that CPU showing at ~45% consistently with the 'top' command after the 464xlat package was installed (it seems to be saturating an entire CPU core (1/2 core on the device). CPU went back to normal after I uninstalled the package, so it looks to me like the device isn't powerful enough handle the IPv4 to IPv6 conversion. For those who are interested in trying the 464xlat package, I had to manually add a new 464xlat interface and make sure it is added to WAN firewall zone to have it working. The default 464xlat interface that get auto added after installation of the package shows not connected, and there's no way to modify the configuration.
Limitation of T-Mobile Home Internet - does not support prefix delegation, so i'm not sure how to get all my subnets to get its own IPV6 prefixes. Additionally, if your IOT devices don't support IPV6, you're out of luck. So my conclusion is if you're buying the GL-XE3000/X3000 to hopefully replace your T-Mobile Gateway and want to support dual stack IPv4 and IPv6 on your network, you're out of luck. The reason why I switched to the GL-XE3000 is so I can force 5G SA since the T-Mobile Gateway G4SE that I have currently only support 5G NSA, and at where I am living, the 4G signal is far worse than 5G, so my downstream is good but upstream is crap, so overall experience is crap especially for working from home.
I hope that helps.