I have managed to get root access with Magisk; however, I can not work out how to unroot my smartphone with Magisk. Resolution:
Magisk is a revolutionary Android rooting tool that, thanks to its modules, allows for easier operating system customization than ever before. The drawback with Magisk is that it’s not a simple task to get root access with it and often there are subtle differences between the tutorials you need to follow, which means no universal guide will suffice. Thankfully, though, uninstalling Magisk is much more straightforward.
The Magisk app allows you to uninstall it directly from within the app itself, and when you do, it will remove root access from the Android operating system completely.
To do this, open the Magisk app and tap on Complete Uninstall. This results in Magisk and all Magisk modules being deleted from the device and root access to the Android operating system being revoked.
See also: Download: Magisk/Magisk Manager
There are some other methods you could use to remove Magisk’s root access as well. These include uninstalling it from the custom recovery image, flashing the original stock boot image, or installing an official over-the-air update. As with Apple iPhones and jailbreaking, if you install an official firmware build by accepting an OTA software update, it will remove the root access. If it doesn’t, you can download the OTA file and install it yourself and it will remove the root access.