https://wccftech.com/download-ios-14-beta-4/

Apple has seeded iOS 14 and iPadOS 14 beta 4 to registered developers with iPhone and iPad. Here’s how you can download it.

Beta 4 of iOS 14 and iPadOS 14 has been seeded to developers and it arrives a couple of weeks after the third beta was made available on the developer portal. As ever, this is a bug fix and performance enhancement release, which means you should go ahead and download it right now.