App Library keeps switching around. From my preset order to a different order after the latest update

App Library cannot be set in any order. It's not customizable. There is no order you can set it to it at all. So nothing has changed.

Apps in are sorted by type into groups, and then ordered alphabetically within the groups.

Your personal Home Screen app organization has not changed and remains in whatever order and layout you have it.

App Library organization is entirely independent to your Home Screens.

I have 14 categories. The Groups depend on the apps installed. if you are adding and removing apps or apps are getting offloaded categories may change or disappear if there are no apps that fit into a particular category.

The App Library is dynamically generated, so there can be changes to it some times.

Also, if developers change the category for their app in an update it may affect in what group they get placed.

In reality, there's really nothing you can do to control the App Library.

I'm having this same problem on iPhone 11 iOS 14.4. My App Library keeps changing between the "normal" library with all of my apps and their categories to a very simple library only showing Apple apps. It randomly changes between the two throughout the day.

Here's a photo of what it looks like now with just Apple apps in the library categories.

I am having the same problem too. It just switches around from time to time. Sometimes all the other apps are in the Other folder and only Apple apps are in the right categories, other times all the apps are sorted.