Is NEDNSProxyProvider supported on macOS?

Is NEDNSProxyProvider supported on macOS?

But on this page it says

Code Block 
Looking for an extension with identifier com.blob.macappproxy.dns and extension point com.apple.networkextension.dns-proxy
Failed to find an app extension with identifier com.blob.macappproxy.dns and extension point com.apple.networkextension.dns-proxy: (null)

Code Block 
func request(_ request: OSSystemExtensionRequest, didFailWithError error: Error) {
      os_log("System extension request failed: %@", error.localizedDescription)
      status = .stopped
}

Code Block 
@IBAction func startFilter(_ sender: Any) {
    status = .indeterminate
    guard !NEFilterManager.shared().isEnabled else {
      registerWithProvider()
      return
    }
    guard let extensionIdentifier = extensionBundle.bundleIdentifier else {
      self.status = .stopped
      return
    }
    // Start by activating the system extension
    let activationRequest = OSSystemExtensionRequest.activationRequest(forExtensionWithIdentifier: extensionIdentifier, queue: .main)
//    NSLog("bundleIdentifier: " + extensionIdentifier)
    activationRequest.delegate = self
    OSSystemExtensionManager.shared.submitRequest(activationRequest)
     
    self.update {
      self.manager.localizedDescription = "DNS Proxy"
      let proto = NEDNSProxyProviderProtocol()
      // proto.providerConfiguration = +++
      let data: [String: Any] = [
        "key1": "example value 1",
        "key2": "example value 2",
        "items": []
      ]
      proto.providerConfiguration = data
      proto.providerBundleIdentifier = extensionIdentifier
      self.manager.providerProtocol = proto
      self.manager.isEnabled = true
    }
  }

FYI I have SIP disabled.

Code Block swift
class ViewController: NSViewController {
	var manager: NEDNSProxyManager?
	private func installSystemExtension() {
        let request = OSSystemExtensionRequest.activationRequest(
            forExtensionWithIdentifier: "bundle.id.to.your.NEDNSProxyProvider",
            queue: .main
        )
        request.delegate = self
        OSSystemExtensionManager.shared.submitRequest(request)
    }
    private func configureProxy() {
        
        guard let dnsManager = manager else { return }
        dnsManager.loadFromPreferences { error in
            precondition(Thread.isMainThread)
            
            if let nsError = error as NSError? {
                /* Handle error */
                return
            }
            let proto = NEDNSProxyProviderProtocol()
            proto.serverAddress = "localhost" /* Just for testing purposes */
            proto.providerBundleIdentifier = "bundle.id.to.your.NEDNSProxyProvider"
            dnsManager.providerProtocol = proto
            dnsManager.isEnabled = true
            dnsManager.localizedDescription = "Testing DNS Proxy"
            
            dnsManager.saveToPreferences { saveError in
                if let nsError = saveError as NSError? {
                    /* Handle error */
                    return
                }
                /* Handle Success Case */
            }
        }
    }
}
extension ViewController: OSSystemExtensionRequestDelegate {
    
	/* Other delegate methods here */
	func request(_ request: OSSystemExtensionRequest, didFinishWithResult result: OSSystemExtensionRequest.Result) {
        switch result {
        case .completed:
            manager = NEDNSProxyManager.shared()
        case .willCompleteAfterReboot:
         	/* Proceed with result here */
        @unknown default:
            /* Proceed with result here */
        }
    }
}

Code Block 
import Cocoa
import os
import NetworkExtension
import SystemExtensions
class ViewController: NSViewController {
  override func viewDidLoad() {
    super.viewDidLoad()
    os_log("DNSFILTER: viewDidLoad")
    installSystemExtension()
    configureProxy()
  }
  override var representedObject: Any? {
    didSet {
    // Update the view, if already loaded.
    }
  }
   
  var manager: NEDNSProxyManager?
  private func installSystemExtension() {
    os_log("DNSFILTER: installing system extension")
    let request = OSSystemExtensionRequest.activationRequest(
      forExtensionWithIdentifier: "com.blob.macappproxy.dns",
      queue: .main
    )
    request.delegate = self
    OSSystemExtensionManager.shared.submitRequest(request)
  }
   
  private func configureProxy() {
    os_log("DNSFILTER: configuring proxy")
    guard let dnsManager = manager else { return }
    dnsManager.loadFromPreferences { error in
      precondition(Thread.isMainThread)
       
      if let nsError = error as NSError? {
        os_log("DNSFILTER: Failed to load the filter configuration: %@", nsError.localizedDescription)
        return
      }
      let proto = NEDNSProxyProviderProtocol()
      proto.serverAddress = "localhost" /* Just for testing purposes */
      proto.providerBundleIdentifier = "com.blob.macappproxy.dns"
      dnsManager.providerProtocol = proto
      dnsManager.isEnabled = true
      dnsManager.localizedDescription = "Testing DNS Proxy"
       
      dnsManager.saveToPreferences { saveError in
        if let nsError = saveError as NSError? {
          os_log("DNSFILTER: Failed to disable the filter configuration: %@", nsError.localizedDescription)
          return
        }
        /* Handle Success Case */
        os_log("DNSFILTER: dns proxy configured")
      }
    }
  }
}
extension ViewController: OSSystemExtensionRequestDelegate {
  func request(_ request: OSSystemExtensionRequest, actionForReplacingExtension existing: OSSystemExtensionProperties, withExtension ext: OSSystemExtensionProperties) -> OSSystemExtensionRequest.ReplacementAction {
    os_log("DNSFILTER: Replacing extension %@ version %@ with version %@", request.identifier, existing.bundleShortVersion, ext.bundleShortVersion)
    return .replace
  }
   
  func requestNeedsUserApproval(_ request: OSSystemExtensionRequest) {
    os_log("DNSFILTER: Extension %@ requires user approval", request.identifier)
  }
   
  func request(_ request: OSSystemExtensionRequest, didFailWithError error: Error) {
    os_log("DNSFILTER: System extension request failed: %@", error.localizedDescription)
  }
   
  /* Other delegate methods here */
  func request(_ request: OSSystemExtensionRequest, didFinishWithResult result: OSSystemExtensionRequest.Result) {
    switch result {
    case .completed:
      manager = NEDNSProxyManager.shared()
    case .willCompleteAfterReboot:
       os_log("DNSFILTER: willCompleteAfterReboot")
    @unknown default:
      os_log("DNSFILTER: default")
    }
  }
}

Code Block 
2021-03-18 17:09:27.676100+1100 macappproxy[1142:14431] DNSFILTER: viewDidLoad
2021-03-18 17:09:27.676187+1100 macappproxy[1142:14431] DNSFILTER: installing system extension
2021-03-18 17:09:27.678794+1100 macappproxy[1142:14431] DNSFILTER: configuring proxy
2021-03-18 17:09:27.922090+1100 macappproxy[1142:14431] DNSFILTER: System extension request failed: The operation couldn’t be completed. (OSSystemExtensionErrorDomain error 1.)

Code Block 
import NetworkExtension
import os
class DNSProxyProvider: NEAppProxyProvider {
  override func startProxy(options: [String : Any]?, completionHandler: @escaping (Error?) -> Void) {
    // Add code here to start the process of connecting the tunnel.
    os_log("DNSFILTER: provider started")
    completionHandler(nil)
  }
   
  override func stopProxy(with reason: NEProviderStopReason, completionHandler: @escaping () -> Void) {
    // Add code here to start the process of stopping the tunnel.
    completionHandler()
  }
   
  override func handleAppMessage(_ messageData: Data, completionHandler: ((Data?) -> Void)?) {
    // Add code here to handle the message.
    if let handler = completionHandler {
      handler(messageData)
    }
  }
   
  override func sleep(completionHandler: @escaping () -> Void) {
    // Add code here to get ready to sleep.
    completionHandler()
  }
   
  override func wake() {
    // Add code here to wake up.
  }
   
  override func handleNewFlow(_ flow: NEAppProxyFlow) -> Bool {
    // Add code here to handle the incoming flow.
    return false
  }
}