I checked that just to ensure there was no background updates occurring, and at the moment my PC is the only thing connected, we disconnected all devices to check if it made a difference and it didn’t.
@Wildcard as @Keith_Beddoe suggested, setup a PPPoE connection from your PC to the ONT and see how that performs.
Have you changed the speed and duplex settings under network adapter?
If you don't know how look on YouTube but set it to 1gbps and your pc should be much faster on a speedtest.