Well, javascript is mutable so technically nothing is immutable. But I'm referring to working with React's hooks, where all props and state should be treated as immutable except for refs.
Refs are just as immutable in that perspective. And no, you're not supposed to mutate ref.current.anything outside useEffect or a callback or similar...
Of course you can! That's the whole point of refs, and why you can't use them as a dependency to callbacks or effects. They're totally mutable, which makes them very tricky to deal with. I mean, I wouldn't recommend updating them outside of effects/callbacks, but it's valid. For example: you can make a ref to count the number of times React calls your render loop by updating it in the body.
