It isn't hard to find some numbers that will cause SwiftUI to break down a little

BreakingSwiftUIList.swift

struct Item: View, Identifiable {
  let forInt: Int
  var id: String {
    return "\(forInt)"
  }
  var body : some View {
    //: Make this view more complex
    HStack{
      Text("\(forInt)")
    }
  }
}

struct SimpleList : View {
  //: Increase this number
  static let max = 100
  let list: [Item] = {
    var allItems: [Item] = []
    for i in 0...max {
      allItems.append(Item(forInt: i))
    }
    return allItems
  }()
  
  var body: some View {
    List(list) { item in
      return item
    }
  }
}

It isn't hard to get yourself to a point where you break a List in SwiftUI. It is trivial to program this to see the limits. Anything would break with a list this large contained only in memory though. There is a point where reference types are required to simply handle the load within memory constraints, and databases are need for record keeping to give us a count of objects. This is where NSFetchedResultsControllers shine