I haven't used the list node for net_radio, only Tidal and local DLNA. But net_radio is much simpler as it doesn't have a deep hierarchy. What I did in my house is use the Musiccast app to save each radio station to a preset. Then, I use the [input] node "recallPreset" command to select each one by number.
The [list] node is really complicated to set up for browsing media as all network services have a different standard for how they arrange files. It's just not straightforward so I avoid it if possible. But if you want to try it, there is a basic example workflow in the collection that demonstrates browsing for Tidal.
I don't have one of those speakers so it's not something I've able to test. I use WXA-50s across my house and they work fine but I believe the stand-alone speakers have a much simpler set of features. Remember that every API call is in the collection but that doesn't mean each one works for every device type. The only way to know is to try it. Please let me know how things work out for you!
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Vahdettin