shk292:
Yes, the M5s definitely have gigabit ethernet ports, but they seem to limit WAN throughput to around 500Mbps. If I connect the ISP-supplied router to the ONT I can get the full gigabit but I prefer to have the M5 in router mode in order to be able to use the other features such as AV and family controls.
Saw something about that while I have been looking:
https://www.tp-link.com/us/support/faq/2429/
Disabling QoS settings was suggested. (point 3 in the link)