LAN connections don’t really need to be ‘secure’ unless you know you have people that are going to listen in on your wireless… If that’s the case you have bigger problems than this.
Also, are you compiling your own code via Arduino IDE (or similar)? Why not look into something like ESPEasy.
WLAN or LAN, doesn’t matter. For either to be snooped an attacker would need access to your system or some serious time and effort.
Still, if you’re not having guests on your wifi and you’re using a proper password you don’t need to secure the local connections. Its just not necessary.
ESPEasy does all the over head for you. Is a precompiled firmware that allows you to connect in to your network. Its just a matter of a few changes in configuration and you’re up and running.