Well, those are crazy high speeds. That bandwidth is to allow multiple concurrent high-speed end-points and some 4K/Atmos movie steaming missed-in. This is what my wired-gigabit-ethernet Aurora-R6 gets on Spectrum cable. It is considered good. SpeedTest.net 9-23-2022 350 Mbps DL (96 ms DL-latency)11 Mbps UL (96 ms UL-latency)22 ms Ping (Idle latency) If you really want to spend time/effort on trying to get it to go faster ...a. First, be sure it's not the CAT-6 (or better) ethernet cableb. Try re-config of Killer drivers and services in Killer Control-Panelc. Turn-off most-or-all features/services in Killer Control-Paneld. Uninstall all existing Killer drivers and Apps and use whatever Windows-11 tosses you. For "Try re-config of Killer drivers and services in Killer Control-Panel" above ... be sure to try Turning-off Auto-Bandwidth by setting to Manual with 950 down and 950 up .   
I get consistent downloads around 950mbps but uploads are always around 210mbps. The pc is connected directly to Arris router provided by Frontier FIOS. The router reports the two speeds to be roughly the same. A second Win10PC connected to a separate port gets almost the same speeds both up and down around 950mbps. The 8950 has the  Killer E3100G 2.5 Gigabit Ethernet Controller with driver version 1125.8.515.2022 installed. The system has the Killer Ethernet Performance Driver Suite UWD installed. Dell Support reports the drivers to be up to date for the Win11 Pro system.  Any ideas appreciated KentM
XPS 8950, Ethernet, slow uploads