T-Mobile 5G Home Internet & TP-Link Deco Mesh WiFi System (Deco S4)

I am in the process of setting this up, except with Deco m9.

The way I have things set up with Spectrum: The cable modem functions as a modem only (I turned off NAT/routing functions) and is connected via Ethernet directly to one of the Deco base stations. The Deco does all the router functionality. I like this setup because the Deco app is quite nice.

I got an Arcadyan KVD21Gateway from T-Mobile. I tested it and download speeds are ok, upload speeds are very mediocre. From everything I can see so far, I cannot turn the T-Mobile Wi-Fi Gateway into a simple modem and use the Deco as router which is unfortunate. I'll have to use my Deco as dumb access points in order to avoid double NAT.

I'll still finish set up and try it out. I'll report back.