The #1 thing would be expert javascript skills and comfort jumping between frameworks - so someone who spent a few years on angular and did great work and understands fundamentals would be A-OK, especially if they had some hobby exposure to react.
You may have some misses with people that index very high on react but not as great on the underlying fundamentals...they tend to have issues with preferring the hot/cool thing over the right thing for the job.
Especially in enterprise a lot of great javascript engineers are stuck in angular code bases, but great at react that was the main takeaway - when looking for react engineers not to over-index on react experience specifically
Here are some questions to ask: https://www.edureka.co/blog/interview-questions/react-interview-questions/
As well as an overall guide:
1) Good aptitude
2) Coding test... give candidate some existing code and ask to add a feature (face-2-face) e.g. add a sorted/paginated table, or chart, etc. and what backend API would be required for it.. something which shouldn't take more than hour to implement.. person should be able to google to find solution/code..
3) Basic debugging skills. Knows how to find issues via Chrome inspector if things are not loading.
4) Good JS skills..
5) React questions..
Last 2 are entirely skippable if the person passed first 3.. because most people use google/stackoverflow to get things done.. adding 4 and 5 would just take longer to find the right person..
You can also send a simple take home (ie/ re-create this static webpage using React) which weeds out bad code quickly. After that, follow-up with more detailed questions during the on-site to see if they have the broader exposure and mindset that you're looking for (ie using the right tool for the right job). You should focus more on finding someone who could jump in and start writing great code, and good at learning new frameworks quickly.