You know, I don't have much of a clue about what you are saying. My reference to Plex connect and openplex was probably more a reflection of my own confusion, don't castigate me for it. Almost everyone else has a better understanding than I do. Who's downgrading cores? Not me, so I'm not sure who you are addressing those remarks to. perhaps a new paragraph would have clarified. I have two AppleTVs, a 2 and a 3. I don't get reboots any longer on the 2, using the Plex app. I don't care that its not supported anymore, it works for me.
Plex Connect is not working since Netflix arrived because plexconnect needs the IP of the plex server (hardly surprising) and Netflix needs to connect direct to the internet and rejects the IP set for plexconnect. So you csan have one or the other but not both. For now, I am choosing to run Plex on my old ATV2, and Netflix on my ATV3. Or both on my Samsung hub. Depending on my mood.
And, just to clarify... I'm so addicted to Netflix and Stan (Australian stream) that Plex has taken a back seat this week, and probably will continue to, for some time to come.
Both Plexconnect and Netflix work for me in Australia, so you must have an issue with the DNS server being used by Plexconnect to forward requests. Are you using the default 8.8.8.8(Google) or your ISPs?