The beta phase for iOS and iPadOS 15.3 is over, so it’s not surprising that Apple is working directly on the systems.
Anyone who has installed the beta profile on their iPhone or iPad can proceed directly with testing, because there is a first beta of iOS and iPadOS 15.4
You have to look for new functions, at the moment the changelog is silent about innovations in the systems. If there is anything interesting to be found, we will of course discuss it with you here.