Look at the picture. There is no longer a mix RGB in the shader editor. It wasn't like that a few days ago. What tha hell happened?? No mix RGB
The node was renamed to Mix Color.
That is what I thought. Is it any better?
You can change it from Color to Float (then it becomes a Math Mix Node) or Vector (then it becomes a Vector Mix).
It's more a visual 'upgrade' than a functional one, although the Vector version also has a non-uniform mix factor.