I could have sworn that there was a GUI under the Neovim organization that uses Qt. Maybe I am misremembering things?
Neovim-qt (which is an external project) is bundled with the official Windows distribution – maybe you were thinking of this?
There’s also GitHub - neovim/python-gui: Proof-of-concept Nvim GUI. Not maintained., which I don’t have to comment because the link title says it all 