Extend pc monitor on 2020 generation tablet, by cable
Tablets are not designed to show display signals for e.g. a PC. Usually a tablet don't has any hardware support for receiving display signals. 

Hence everything has to be transmitted via IP for example as video stream. Video encoding and decoding comes at a price that the latency is much higher that a standard HDMI or DisplayPort connection which mostly transmit uncompressed data.

If you have problems with your Wifi connection you can try to use the USB connection via ADB to establish a IP connection between your PC and the tablet. In detail the following command allows you to connect a TCP port on-device with a TCP port on your PC:

adb forward tcp:5000 tcp:5000


Therefore if you configure a remote screen software to use the port specified here as forwarded port (or change the port forwarding to match the used tcp port on the software) you can get a Wifi independent connection.