The Dune series has six novels, the final one is Chapter House Dune, which does in fact end mid story.

I know this because I read them in the 90s and didn't realise that Frank Herbert was dead for quite some time after reading Chapter House.

I know that, I've read them too. In the SP, and in this thread we're discussing endings to novels. No one is complaining about a series that isn't finished due to the author's death.