Interesting question. I don't have a clear answer.
Depth can help you standout in the interviews. Breadth can help you get shortlisted for the interviews.
Learning backend development in more depth is what I would do in your position. I would also spend a lot of time on interview prep (DSA first then LLD if time's available).
Learning React and becoming full stack might help you get shortlisted in a few more opportunities than with just backend. But converting those opportunities as a fresher with relatively lower depth of skills could be difficult.