Are you sure the shared Ethernet works? Ethernet takes priority above WiFi. Activate airplane mode on your PC (that is, turn off WiFi) and see what happens. Since you don't want to use the WiFi you can keep this setting.
My PC and Xbox One connected to ethernet from the wall (shared apartment complex) prompts me to login to an unknown linksys WAP1200AC wireless access point (probably a neighbour's?). Any way to fix this myself?
EDIT: It works now and I have no idea why...

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