When I first received my Extreme in early 2020, it came standard with a Startech PCIe fiber card and Emile's default recommendation at that time was to go with fiber using Startech SFPs and so not really "tweaking" to start with fiber back then.
When the disastrous Roon update was released in 2020, it was most disastrous for those of us who were on fiber and according to Emile, it was because of the higher power draw of fiber and so I switched to copper. It was on copper that I did most of my network tweaking and it drove me nuts that I could hear tremendous differences amongst different copper Ethernet cables, switches, routers, and modems. How was anyone to know what true "neutral" sounded like? I discovered what I felt was true "neutral" when I disconnected the Ethernet cable from my Extreme and so that became my new reference point. When TAS was released, because it was not network chatty like Roon, the network was no longer the noise jungle it once was and so disconnecting from the network no longer made much difference but because I could still here differences between fiber and copper, in my mind, the network was still not completely transparent and so I continued to disconnect.
With the new update, it's become clear that we have entered a new era with our Extremes and "best practices" have changed. Not only does copper sound uniformly better than fiber (due to higher packet noise according to Emile) but for reasons that are mysterious to me, copper now sounds uniformly better than "disconnecting" from the network and so perhaps it would be helpful, with Emile's assistance, to discuss what we currently know about "best practices." Emile, please correct me if I have misunderstood anything.
1. Avoid fiber
2. Avoid disconnecting from the network
3. Avoid tweaking network settings (i.e. no static IP)
4. Ethernet port 1 potentially sounds slightly better than port 2
5. Cheap, long CAT5 unshielded UTP cable is what sounds best. UTP data pairs are transformer decoupled twice and is preferable to STP. Unshielded sounds better than even a floating shield. Longer sounds better than shorter. I recall Emile is using 45 meters of cheap CAT5 unshielded UTP cabling to his Extreme and so maybe something like the following sounds better than any audiophile cabling?