sadly it appears that they all but have. so many projects out there decide that Discord should be the only way to discuss development, report bugs, or offer tech support.
It is. Slack and Discord didn't kill forums, Reddit did. Because Reddit is a mega-forum. Instead of creating a specialized forum somewhere on a website you need to maintain, it's easier to just create a subreddit. Bam, new forum!
And we're discussing the disappearance of forums on a forum...