How to hide the App Library
There's no way to fully hide the App Library - Apple doesn't allow it. But you can make it much harder to access by adding empty Blank Spaces widgets to the pages between your home screen and the App Library. This stops the mindless swipe-to-browse habit.
Add buffer pages
Swipe to an empty home screen page
Long-press on an empty area until the apps start to jiggle
Tap Edit (top left) > Add Widget
Search for "Blank" (look for the minus sign logo)
Pick an unused widget (like Widget 5) and tap +
Repeat on another empty page
Having the App Library at least 2 pages away from your main screen makes a big difference. Instead of swiping straight into your full app list, you'll just see a blank page.