I finally stopped using my AirPort Extreme as a router. Now I just use my several AirPort Extremes as access points, and let my internet gateway be the router, the reason being I just moved up to a 10 GbE Mac mini M4 on 1.9 Gbps internet service. Most of my home network backbone is still Gigabit, and that's what the AirPort Extremes hang off of, but there is a dedicated CAT6* line going from the modem in the basement to the Mac mini in the home office on the second floor.
I still love the AirPorts Extremes at access points though, since they're so stable and they work so well with Apple devices, even brand new ones (like recent iPhones, my iPad Pro M4, etc.). So, over the years, I've been slowly collecting them cheap on the used market to build out the coverage on my large and oddly shaped house, and to build out the WiFi network into the backyard too. Here is my current setup:
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I've actually run outdoor CAT6 into the yard into the cabane and to the gazebo. Fortunately, the guy who built the house ran power to both. The two AirPort Extremes work just fine through our Canadian winters.
*I had two runs from the basement to the 2nd floor home office, one being CAT5e and the other being CAT6. My M1 Mac mini was running off the CAT5e fine on Gigabit. After I swapped in the 10 GbE M4 Mac mini, it initially negotiated fine at 2.5 Gbps, but I noticed it later dropped down to 1 Gbps. I've since switched it over to the CAT6 line to ensure stability of the connection.