In my opinion, people mix React + jQuery a lot. Some of them use jQuery to do Ajax calls (habits?). Some use jQuery to deal with CSS property changes (CSS is unresolved!). Some use jQuery for modal dialogs (Catching outside clicks.).
But React + Vue I think I saw only a demo app. Ryan Florence only showed how to replace Angular by converting an existent codebase, step by step, component after component, to demo how easy it is to integrate React into virtually any code base. But is it used out in the wild? Maybe but never saw something or never read something about such mixtures.