x14, using aw1022 2.5gbe adapter but unable to obtain full speed

I'm using an Alienware aw1022 adapter connected to the thunderbolt port of my Alienware x14 but unable to obtain a decent speed. I've also tried a Ugreen 2.5G ethernet adapter and obtained similar speeds. My Asus router is showing 1805Mbps Download and 1958Mbps Upload as the connected internet speed. I have the adapter connected via a Cat 8 cable to the 2.5G port on the router. I've run speedtest by Ookla and I can only reach 483Mbps Down and 504Mbps up, event though both adapters are rated 2.5G. I've updated to the latest drivers for both adapters and tried adjusting the transmit and receive buffers and URBs in the advanced settings with limited success. Any thoughts as to why I can't obtain higher speeds with the adapter? TIA