Couple of things to add; Ethernet doesn’t work either. Same issue, connects to the network but not the internet. I’ve ordered a wifi adapter for the Xbox that will work with 5gh networks, I’ll be trying that tomorrow. 

Max MTU I have seen get through TMO unfragmented was 1440, but you may need to set it at 1420 depending on what all goes on with your network.

Not familiar with the XB line of consoles, but on the PS line you get the option to set a static value when you step through the network settings manually.

Is there any way to set the MTU on the trashcan? I haven’t found that setting, and I’ve read it’s not available to change. 
 

I’ve tried setting up the network manually and get the same error. 

Probly not available in their firmware.

I have it on my Asus router.  In the WAN section, down around the DNS options.

Sounds like an excuse to upgrade my Xbox lol. I haven’t heard of anyone with a one or x/s have these issues. Or I’d have to get another router, hook it up to the trashcan, and get the Xbox to connect through it.