The Core lives on (another ) Windows LTSC machine. Defender has Roon.exe and RAATServer already entered for inbound, and I added outbound for private networks.
The Core cannot see the Opensuse workstation, but can see another (and everything else) Windows 10  PC with its DAC is visible, as well as a Lumin U1, which there’s nothing to setup on, works right out of the box. I can select any of these zones to play on and Roon works OK.
To allow services to pass through the Opensuse firewall, they must be listed first. I can see roonbridge.service is running using the [sudo service --status-all] command, but now to find out how to add the roonbridge service to the firewall list to allow it through.
The whole idea is eventually to setup a simple PC with Linux that can emulate the functions on a Lumin U1 (mini) on a Roon Network. From the experience so far, it’s not simple with Linux other than to install it in the first place. Setting up Linux from scratch is not a trivial task. In particular, the built in drivers for the laptop hardware is far from optimal, where the previous windows build was a lot more responsive albeit with a larger overhead, go figure. I thought OpenSuse being controlled by a company would have yielded some better results over a community type distro, but Linux, the way it is will be only on very small amount of desktops, since it’s such an ass to setup.