Some have been leetcode, others just asking esoteric react facts.

The in-person rounds I've done have seemingly gone well, I've produced code that fits requirements each time.

Not exactly sure.

Have you asked any of the interviewers for feedback / why they passed? Can’t fix what you don’t know.

They've given some - all I've really received is "your solutions were interesting and passed the bar, but we proceeded with another candidate"

I never understood the interview questions around what you would call "esoteric facts" about specific frameworks. This tells you nothing except that the candidate is good at cramming, and knew what they needed to cram for.

Now if it's "open book", and the idea is to see how efficient the candidate is at finding the answer, that makes more sense to me.