6 hours ago, PineyCreek said:
10/half sounds like an auto-negotiation failure to me assuming a good cable and cable connection.
After further testing, I came to the conclusion that the switch was being weird.
I had to manually set the connection to 100 MF on the switch for TV to negotiate properly, but even after that, the download remained below 10 Mbps, while upload reached around 80 Mbps.
Eventually, I decided to reset the switch to its factory settings. After setting it up again, all the devices, including the TV negotiated properly.
Now the TV seems to get the intended speeds. Both Plex and Netflix are working fine.
And after upgrading its Ethernet drivers, the secondary PC also reaches the desired speeds.
So... problems solved, I guess.