How can I turn off Split View on iPad mini 6

Unlike iPadOS14 and earlier versions, multi-tasking cannot now be disabled from settings. Multi-tasking has received a significant overhaul, both simplifying its use and introducing new controls. 

Key to accessing and controlling (or avoiding) multi-tasking is the small “three-dot” button that is found at the top-centre edge of the visible App windows. 

More information about using multi-tasking can be found in this support page:

Use multitasking on your iPad - Apple Support

The iPad User Guide is also a rich source of information about using iPad and its many features. The Guide is available both online using a web browser (such as Safari), or as an Apple Books download:

iPad User Guide - Apple Support

https://books.apple.com/book/id1567104892

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copied from: Use split screen in Safari on your iPad - Apple Support