sometimes without visible apps (apps are still there but the thumbnails are invisible).
Try this -> if you are using Screen Time, go to Settings -> Screen Time -> Content & Privacy Restrictions -> iTunes & App Store Purchases -> Change Deleting Apps to Allow.
About storage, see this Apple articles below:
If you need more space for an update on your iPhone, iPad, or iPod touch
https://support.apple.com/en-us/HT203097
How to check the storage on your iPhone, iPad and iPod touch
https://support.apple.com/en-us/HT206504
Clear Other storage on your iPhone or iPad
https://support.apple.com/en-us/HT211686
What's the difference between device storage and iCloud storage?
https://support.apple.com/en-us/HT206504
What does iCloud back up?
https://support.apple.com/en-us/HT207428