This is really weird. I usually view Facebook on Safari on the MacBook or the iPad, but sometimes I use Chrome on the Mac and I forget why I began doing that. There was something that Chrome did better, no idea now what it was.
ANYHOO ... I just now checked Facebook on Chrome, and every post in my feed is from the group "My Cat is an Asshole" which I joined a few days ago. Every post. I refreshed the browser to make sure that I was indeed in my feed and not on their page by mistake. Nope. Every post. As far down as I scroll. I came back to Safari, went to Facebook, and all is normal. Or as "normal" as Facebook gets.