I have a CAT 6 Ethernet cable and my motherboard has WIfi 6 and it says it can go up to 2.4gbps and everything is plugged in correctly and my Speed and Duplex is set to Auto Negotiation.
You're confusing a few concepts here.
Ethernet cable and WiFi....you use one or the other, not both.
Preferably the ethernet
"says it can go up to 2.4gbps"
"2.4" is the frequency, not the speed.
2.4GHz.
Cat 6...this is almost certainly your problem.
Very likely a faulty or non-standard cable.
Try a good quality Cat5e, see what happens.
And also, what specific router model is it?