Sadly the Corel groups here in Deviant Art and less than 6. And we don't seem to be unified and active all the time.
For what you're seeking it would be best to create an account directly with the Corel website, under their Painter community.
It is mostly made of professionals and the amateurs seem to stick to the Painter Essentials part.
Here is the link, I hope this helps.
painterfactory.com/