Correct. This was implied when following the flows, but you’re right, this needs to be called out because the write up is meant to also help users that don’t happen to be network engineers.
This write-up isn’t really meant for consumer equipment. Although someone running WRT firmware might have access to the feature-set needed to segment with VLANs, enable multi-cast, and support MDNS, most consumer grade networks are typically a single segment with maybe a wireless repeater or two tossed in there. That’s not to say that there are not people out there with multiple WRT routers segmenting their network, but I think its a fair assumption that the likelihood (and number) of users doing it this way is smaller than the crowd using pro-sumer, SOHO, professional/enterprise, or opensource.
I’m not seeing ICMP to the whole subnet, but theres definitely traffic being sent by the core to the subnet broadcast IP the core is in. I didnt grab packet captures looking at the remote/bridge either, so I can’t say if thats occuring from them.
I’m rather new to Roon so forgive the question, but what do you mean by endpoint? Is that the device that sends the sound to the speakers? If this is the case, then that is in the core traffic flow listed as the bridge (along with the remote), and broken out at the TL;DR. Let me know if that needs further clarification.