I logged into Telegram yesterday and just saw the channel was closed too. I was pretty disappointed myself as I didn't know that was the plan. I've reached out to the TrueOS devs and let them know that I'd be happy to keep the channel open and maintain it myself but I have not received a conclusive response back to my messages.
TrueOS is still under active development but we don't have the need to blog nearly as much these days. I'll ask the devs if there's an updated roadmap and will pass the message along when I hear back.