These devices have the wifi/ethernet bridge functionality being discussed, (as well as a bunch of other stuff) and are OpenWRT based. Built in openvpn/wireguard as well. We bought a bunch for our team way back when (IIRC they were < $20 USD then) Gl.iNet has other similar more powerful devices as your use case may need.
Pre-made wireless bridges generally have web interfaces (and/or dreadful phone apps) to get them set up and chatting the right way.
It's a process that's very similar to that of configuring a home network router, except the bridge works in the opposite direction.
In this way, the devices with ethernet jacks have no idea what things like WEP, WPA, or wifi even are. And that's kind of the whole point. :)