Specifics ports for chat on XBox One that can be QoS/DSCP prioritized?

You would need to do this at the network level on your Local network. I would assume one of the UDP ports is used for voice. If you really want to know what port is being used you need to run wire shark on your network and do some packet inspection. I did
google but nobody seems to have done this in the past.

If you have a firewall or network hardware, such as a router, you might need to make a configuration change in order for your Xbox One console to communicate with Xbox Live. This configuration change is sometimes called "opening ports" or "port forwarding."
Xbox Live requires the following ports to be open on your router:

• 
  Port 88 (UDP)
  
• 
  Port 3074 (UDP and TCP)
  
• 
  Port 53 (UDP and TCP)
  
• 
  Port 80 (TCP)
  
• 
  Port 500 (UDP)
  
• 
  Port 3544 (UDP)
  
• 
  Port 4500 (UDP)
  

Sorry, no solution. My guess is that Microsoft is applying some kind of QOS to the connection that prioritizes chat so that it isn't interrupted by other traffic. I've noticed that even downloading demos has no effect on the party chat. While in theory this
is a good idea...in the real world you want the game traffic prioritized. Especially in FPS games. QOS will also add a small amount of lag just due to the packet processing.

Game chat definitely doesn't prioritize the chat channel. The quality difference between the two is very noticeable.

check your router settings. your router may be set to prioritize your internet traffic. specifically check your Qos settings

I have tried to raise the same issue with Microsoft Support, however, they play the "There is an issue with the streaming service card..".

This is not the case, I have tested everything on my network and confirmed that these streaming services are specifically not working on the Xbox One.

It is due to their latest update which includes their "QoS settings". This update was installed on my device today and non of the streaming services have worked since. I have requested that they roll this back for my device, however, they have advised that this is no possible.

You would think they would roll back the update since it is causing issues with paid streaming services and costing users money. And, if not, they could at least include the option to uninstall updates on the device.

I have completely reset my router, setup port forwards, confirmed that there are no NAT rules causing issues. Tested the streaming applications on other devices and confirmed that these are all working. I have run all the connection tests from the xbox as well as from the streaming services themselves. These all came back without any issues, however, when you try to play anything on them a generic connection issue error appears.

The QoS settings are disabled by default, I have tried turning on both of the QoS options and still have the same issue. Its clearly to do with this update since this is what they both control:

DSCP TAGGING ENABLED

Differentiated Services Code Point (DSCP) labels are implemented at the IPv4 and IPv6 packet level. This technology is used in wired and wireless networks to detect delay-sensitive network traffic. DSCP labels can be used on networks that support tagged traffic prioritization, such as home routers, QoS-enabled gateways, or ISP networks that support DOCSIS Low Latency.



WMM TAGGING ENABLED

Wi-Fi Multimedia (WMM) tags are added at the wireless packet level and only work when connected to wireless networks. The WMM feature is typically enabled by default on routers and gateways. It protects priority Wi-Fi traffic from latency and throughput in congested wireless networks.

Ok great. Were you able to set the QOS setting to prioritize the xbox?