T-mobile Gateway PC speeds capped at 100Mbps

I am a recent transplant from Spectrum where I consistently had download speeds of around 500Mbps via speedtest.net and switched to T-mobile Home Internet service. Since that time, any other device such as my  cell phone, via wifi gets upwards of 340Mbps through the same T-Mobile Router that my PC is using. With the ethernet cable I seem to be limited to a cap of 100 Mbps.

I have had two T-Mobile technicians pour over the hardware of my PC, say they will call me back with a solution, and never heard from them again. The issue does not lie in any of the hardware or cables that I am using. I am also not unrealistic in expecting the same speeds that Spectrum was able to provide. I simply would like the same download speed as my other devices that I use on the same router on a regular basis. Thank you for your time and consideration.