In my opinion, Material UI is a very much mature and the most popular UI framework for react out there with a veriety of components and new ones frequently released. The support community is huge and welcoming as well. I have presonally build clean and professional looking apps using material ui with less amount of time. Give it a look - material-ui.com
Advantages: Very clean and professional, highly customisable, follows official material design spec. The only downside is that the library when built finally without any optimisations is a bit heavy compared to other frameworks. But there are guides to optimise bundle size and performance of material ui and i think there is a huge future for this framework.