I worried that maybe I'd missed this thread when I posted my own thread on the same error... and then I noticed that this thread is from last April/May.
I get the error in Firefox where I am logged in, and in Edge & Chrome where I am not logged in. It persists if I hit reload.
EDIT: I could get to the Meta forum without problem just now. I have been seeing this problem fairly heavily over the past several days, but never before then. One day recently it was for the 5e Edition, Homebrew and Char Op forums for most of a day.