Besides Apples routers already do a kind of mesh. At the moment I have a Time Capsule in my living room, and I have some stuff connected to it via cable there. I also have a Mac mini and an Apple TV in my bedroom. The Mac mini is connected via cable to the TC in the living room, but since I don't have a switch in my bedroom (yet), and I also have the AppleTV, iPhones and iPad, that I sometimes use in the bedroom, and the signal from the TC is a bit weak in my bedroom, I also have an AirPort Express in my bedroom. That one is NOT connected via cable to the TV, but it extends the wireless network from the TC, so the phones and iPad connects wirelessly to the Express, which sends it wirelessly to the TC. It wasn't called mesh at the time though, but it's kind of a simple mesh, but I would prefer to connect it via cable, since the bandwidth is effectively cut in half.
First my iPhone sends to the Express which forwards wirelessly to the TC. That is TWO wireless transmissions for every packet. The solution is for me to either install a switch in my bedroom or another cable going from the Express to the TC.
The AppleTV 4k is connected via cable to the Express.
As the mini’s plugged, share your internet connection via wi-fi on the mini & use the AP elsewhere?