The downside of mesh is that the wifi point not wired into the ethernet has to have a decent wireless connection. Normally, that would mean the unwired repeater being positioned halfway between you (poor Ethernet) and the wired WiFI point.
To get a signal from a wired location, as you mention, needs a wired access point. If you aren’t sure, a simple router can be an access point, but requires a bit of finagling.
A router usually has about 4 ports that are for the internal network, one for WAN (Wide Area Network, i.e. the internet) and WIFI. A router has DHCP which hands out addresses on the internal network, and also tells those devices, along with their local IP address, where to send communications to the internet - ie., send them to that router.
What you want to do is turn off DHCP: To do this -
Login to the second router, usually by plugging your PC into a local port.
Find the feature when it hands out addresses, and disable it.
Configure the WiFI, either with the same name/password as your main WIFI, or another one.
Change the address of this router so it fits into your main internal network, but does not conflict.
Reboot.
Now you can plug this router into your home ethernet, using a local port. (Be sure to leave the WAN port empty).
NETWORK 101- Too Much Info
Basically, I)P is an address like 10.0.x.x or 192.168.x.x (X is 0 to 255)
Some devices (like routers) have hard-coded addresses
Some ask for an address when they connect to a network or at boot up, using DHCP.
A device talks to any other on the local network directly.
A device talks to the outside world by sending to the “default gateway”. This is why DHCP, along with an IP address, usually sends a “default gateway”.
Most home routers automatically configure themselves to be the one with DHCP handing out addresses, and have a fixed address like 10.0.0.1 or 192.168.0.1.
The “local” ports and wifi will repeat signals back and forth inside the network so the internal devices can talk to each other.
When you disable DHCP on a second router, it does not disable the switching (repeater) function of the device. So it acts like an access point.
Connect this configured second router to the active router (local port to local port ethernet), and any DHCP request from a local port or wifi will carry on to the local port connected to the active router since the second router’s DHCP is off.
When you connect a device to the second router ehternet or wifi, the active router will give any connecting device an address, including to use the active router as the default gateway.
The second router is acting like a switch and access point.
The only gotcha is that often routers have a default address (and often this is 10.0.0.1 or 192.168.0.1) You don’t want your active router and secondary router to have the same address. Change the second router’s last number in its IP so it does not conflict with the main active router or other devices. Perhaps, pick a random number between 150 and 250
Or ask our local nerd to do this for you.