@leif-edh That is doable but you would need to setup WiFi access point on one of those M205 (find a tutorial for hostapd), and enable bridging (available in bridge-utils package).
If you won't use static IP addresses, you would have to also setup a DHCP server on the WLAN and eth, br interfaces.
This tutorial might help you a bit: https://www.cyberciti.biz/faq/debian-ubuntu-linux-setting-wireless-access-point/
Another option is to put a router AP in the middle of it all.
Also, note that the internal wifi antenna does not have much gain and is inside an aluminum box so the range is limited...