Acceptable loading times between scenes?

I am trying to find if there are specific requirements for performance between loading scenes wit, and if tricks like having everything fade-to-black during a heavy (1+ sec) loading time are acceptable or not. We are using the LoadSceneAsync method and loading time still takes a couple seconds of unresponsiveness. Would like to know before undergoing heavier work to amortize level loading across a few seconds.

This would be for being able to get onto the Meta Horizon Store.