When someone uses jQuery in a React project, this is my reaction.
jQuery was initially released in 2006 and is used by most websites, the syntax has become a standard with some developers and people are more comfortable with the syntactic sugar that it provides. When people start with a new React project, its normal for people to add jQuery as well. You know because its handy and we are familiar with it.
But ask any experienced React developer and they will tell you stay away from it as whatever you are trying to achieve with jQuery there is probably a way to do that with React itself. Also it spoils the whole state and prop management of the app when you directly try to modify it without letting the virtual DOM know the changes since jQuery is for manipulating the clients DOM directly. It will be pure chaos. It is not the most lightweight library either.
If you absolutely want to use jQuery then go ahead, there are many people who do this and have no problem. But in a big project having a React first strategy makes sense. Thinking of the $ sign inside React makes me feel there is something wrong and unnecessary.
What to do?
Think of ways you could achieve whatever you want to do with React itself and you will be surprised how much things make sense and look maintainable with React which is not the case with jQuery.