Dumb AP: plugging in a 100Base eth device limits wifi to 100Mbps internet speed

Installing and Using OpenWrt Network and Wireless Configuration
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mk24 is referencing (just as it's seen on your wireless page) - how to describe each connection, it's modulation, rate, etc. This is the chart for 802.11ac (or WiFi 5).

See: https://en.wikipedia.org/wiki/IEEE_802.11ac-2013#Data_rates_and_speed

Example:
screen528

So I assume it's the Netgear?