Upgrading iOS on an old machine is often prohibitive, because many people also worry that the old machine will be slowed down after the upgrade. Youtuber Brando Butch tested iOS 14 Beta 1 under an iPhone 6s and the results were surprisingly smooth.
The new Widget interface and even the new App Library can also be used on the iPhone 6s. There is no problem even using the picture-in-picture function. However, Brando Butch said that the battery consumption rate is relatively fast, and it is unknown whether it is related to the battery being too old.