SwiftUI 2020 + CloudKit + Core Data ZenJournal prototype: https://thezenjournal.com

App.swift

import SwiftUI
import CoreData

let appTransactionAuthorName = "app"

@main
struct ZenJournalApp: App {

    var body: some Scene {
        WindowGroup {
            NavigationWrapper()
                .environment(\.managedObjectContext, persistentContainer.viewContext)
        }
    }
    
    var persistentContainer: NSPersistentCloudKitContainer = {
            
        let container = NSPersistentCloudKitContainer(name: "ZenModel")
        
        // Enable history tracking and remote notifications
        guard let description = container.persistentStoreDescriptions.first else {
            fatalError("###\(#function): Failed to retrieve a persistent store description.")
        }
        description.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
        description.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
        let id = "iCloud.com.idealistspace.zenjournal"
        let options = NSPersistentCloudKitContainerOptions(containerIdentifier: id)
        description.cloudKitContainerOptions = options

        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
        })
        
//        do {
//              // Uncomment to do a dry run and print the CK records it'll make
////            try container.initializeCloudKitSchema(options: [.dryRun, .printSchema])
//            // Uncomment to initialize your schema
//            try container.initializeCloudKitSchema()
//        } catch {
//            print("Unable to initialize CloudKit schema: \(error.localizedDescription)")
//        }
        
        container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
        container.viewContext.transactionAuthor = appTransactionAuthorName
        
        // Pin the viewContext to the current generation token and set it to keep itself up to date with local changes.
        container.viewContext.automaticallyMergesChangesFromParent = true
        do {
            try container.viewContext.setQueryGenerationFrom(.current)
        } catch {
            fatalError("###\(#function): Failed to pin viewContext to the current generation:\(error)")
        }

        return container
    }()
}

NavigationWrapper.swift

import SwiftUI

struct NavigationWrapper: View {
    @Environment(\.managedObjectContext) var managedObjectContext
    
    @FetchRequest(fetchRequest: ZenLog.allLogsFetchRequest()) var allLogs: FetchedResults<ZenLog>

    var body: some View {
        VStack{
            TimelineView(logs: self.allLogs)
        }
    }
}

ZenLog.swift

import Foundation
import CoreData
class ZenLog: NSManagedObject, Identifiable {
    @NSManaged var text: String?
    @NSManaged var createdAt: Date?
}

extension ZenLog {
    // ❇️ The @FetchRequest property wrapper in the ContentView will call this function
    static func allLogsFetchRequest() -> NSFetchRequest<ZenLog> {
        let request: NSFetchRequest<ZenLog> = ZenLog.fetchRequest() as! NSFetchRequest<ZenLog>
        
        // ❇️ The @FetchRequest property wrapper in the ContentView requires a sort descriptor
        request.sortDescriptors = [NSSortDescriptor(key: "createdAt", ascending: true)]
          
        return request
    }
}

Not exactly sure if this is the right way to do it but it worked for me. Remember to add your .xcdatamodelId file to pair with your core data config. Also add the right entitlement for your app including iCloud CloudKit and remote notifications.