Hello,
For this one, you can configure your first RUT240(1) to be on client mode which will then connect to the other RUT240's WiFi, which your Mac is connected to via ethernet.
Here's a link for you to refer to regarding its configuration https://wiki.teltonika-networks.com/view/RUT240_Wireless#Client_Mode
Once it is connected, you need to enable the Remote HTTP access of the RUT240(1) by navigating to System -> Administration -> Access Control. Then go to the "WEBUI" Section and enable the "Remote HTTP Access".
Once done, make sure you click Save & Apply on every configuration.
Now connect to the other RUT240(2) via ethernet, and check the IP of the other RUT240(1) that is connected via Wifi by navigating to Status -> Network -> Wireless. From there, you can check the Wireless clients of your router. Copy and paste the IP address, then paste it on your browser to see if you can access the RUT240(1) without connecting to it directly. Basically, both your Mac and the RUT240(1) are in the LAN network of the other RUT240(2) and can establish connectivity.
Note that by default, if WiFi is the WAN source of your router (meaning it is a WiFi client), then you'll connect to its WiFi Access Point, you can have internet connectivity since our Router can be configured as Access Point and WiFi client at the same time.
Let me know the results.
Best regards,
Robert