[Steam Machine] 2.5Gbit network upgrade

So the standard network interface on the Steam machine is a 1 Gbit link. Let's face it, we can consider this network speed to be "legacy", as most people are in the process of upgrading or have already upgraded their backbones to 2.5Gbit and beyond. Many motherboards do already come with an integrated 2.5Gbit (or even faster) for their networking needs.

With the option to transfer your gamefiles from another computer baked into the Steam Client, we want to have our games installed without too much waiting. With a 1Gbit link you will be waiting 2.5 times longer. For a game like Baldur's gate which is 100+ GB, it is a LONG wait.
For people downloading/running/storing their games on a NAS, this upgrade will also be important to you.

The solution is to replace the internal 1Gbit network port by an external USB 3 adapter. Preferably one that has a Realtek RTL8156 or RTL8156B chipset. Since I had a spare Cable Matters USB A/C 2.5Gbit 202025 which has a RTL8156B chipset lying around, I decided to use that one.

Power down the steam machine. Attach it to the 1 USB C port in the back. Powering down during this process is important because otherwise after every reboot the USB connection will reset itself to 480Mbit speeds. A weird quirk that I was able to figure out after some testing/troubleshooting.
Steam OS recognizes the device and uses the realtek r8152 driver.

Go into desktop mode and check Info center. Make sure the USB device runs at 5000M speed (and not 480M). Doubleclick the network icon in the taskbar and check if the network speed is now showing 2.5Gbit.

If you want to use SSH command line (either local or remote) to check if everything is OK:

lsusb -t
(should show a line saying // Port 001: Dev 002, If 0, Class=Vendor Specific Class, Driver=r8152, 5000M //

nmcli device status
(to check for the device name of the new network dongle, for me it is enp9s0f4u1)

nmcli -f CAPABILITIES.SPEED dev show enp9s0f4u1
(should show 2500Mb/s)

Happy gaming!