https://wccftech.com/dont-panic-ios-14-beta-3-temporarily-disables-3d-touch/

According to the iOS 14 release notes, Apple has temporarily disabled 3D Touch in iOS 14 beta 3. This does not affect Haptic Touch-only devices.

Apple released the third beta of iOS 14 and iPadOS 14 just a while back. And since this is beta software, therefore some weird and wonderful quirks are to be expected. One of them is the unavailability of 3D Touch on devices that support it, which is anything released before the iPhone 11.