Here is the Apple’s IOS 14 Beta 4 offline IPSW where if you can’t install IOS 14 through OTA then this is For your where you can download the IPSW File and install it trough iTunes.

IOS 14 Beta 4 IPSW Download

- iPhone 11 Pro Max, iPhone 11 Pro, iPhone XS Max, iPhone XS18A5342e
- iPhone 11, iPhone XR18A5342e
- iPhone SE (2nd generation)18A5342e
- iPhone X18A5342e
- iPhone 8, iPhone 718A5342e
- iPhone 8 Plus, iPhone 7 Plus18A5342e
- iPhone SE18A5342e
- iPhone 6s18A5342e
- iPhone 6s Plus18A5342e
- iPod touch (7th generation)18A5342e