So far the best alternative that I've seen was Squabbles.io
A lot of communities seem to be moving towards Discord. It has announcements, posts, chat, etc.
I'm surprised there are more Apple TV users than Apple watch users. It always felt like a fairly niched device.
On a somewhat unrelated side-note, as a hardcore Plex user for the last 5-6 years, Apple TV has been an amazing Plex client. Second only to a Nvidia Shield Pro downgraded to 8.2.3 firmware.
Honestly with the quality of their TV boxes, screens and the "ecosystem", I'm kind of surprised they didn't dive into the TV business.