Sorry, I have mixed up USB tethering and Ethernet tethering.

Since you said the Moto G 5G tethers ok with your Win 10 laptop via USB tethering, this sounds like it is not entirely an issue with with the smartphone.

On the other hand, Ethernet tethering is a new feature that came out with Android 11, which allows you to plug a USB-C Ethernet adapter ($15-$20) into your smartphone, then connect an Ethernet cable from the adapter to the router’s WAN port, just like an wireline ISP modem/router. Because it is standard Ethernet, there should not be compatibility problems with the router.

If you reach a dead end with USB tethering, this may be a good option, but first confirm that Moto G 5G supports the “Ethernet tethering” option in Settings → Connections → Mobile Hotspot and Tethering.