You could order an ethernet coupler for testing purposes.

RJ45 Couplers Network Cable Coupler Cat 5 Coupling Lnternet Female to Female Connector Lnline Coupler for Cat5/ Cat5e/ Cat6e/ Cat7 Ethernet Extension Cable(3 Pack Blue) https://www.amazon.com/dp/B088FQB5MS/ref=cm_sw_r_awdo_725FNA3DCC2PQCV7Z586

The thing is you really need to isolate whether the issue is with the PC or the router. If other devices can access the same sites it's not the WAN IP address. Maybe it is a weird wired issue with the G3100. But the only way to know for sure is to test with one of the other PCs and if the issue still persists then bypass the router. I see these routers every day and don't ever seem to run into this issue.