How can I show an alert in an iOS SwiftUI app that the user does not have permissions to access a particular collection?
This question is a bit off topic as it has nothing to do with Realm and is really a coding question about SwiftUI.
A good place to start leaning about SwiftUI is an introduction to SwiftUI tutorial - I suggest Ray Wenderlich’s site as their tutorials are very thorough.
If you have a specific coding question about Realm, please include a short code example of what you’ve attempted so we can get a feel for what you’re attempting to do. Also include more details as well as if this is a local or sync’d environment and if it’s single or multi-user.