RBR40 says no internet, but appears to be connected

This is a new wrinkle which may be interesting to others.  With the yellow (WAN) port connected to the Linux gateway, the router gets a DHCP address correctly.  So, the Linux gateway has two ethernet ports and is configured to pass traffic both ways?  In other words, connecting to this box is similar to connecting to a vendor modem/router?

Those red and green circles on the Orbi "app" are somewhat of a mystery to me.  My guess is that a statellite being "green" simply means that it has a good link with the base station (router) and does not indicate anything about internet status.

I am much more comfortable looking at the Orbi web interface than the "app".  Connect a web browser to the IP of the Orbi router.  The user name is always "admin" and the password was originally "password", but you may have changed it during the setup.

I would look to see what the web interface says about the internet connection.  Things like gateway, DNS, subnet mask, NTP server, etc.