Publishing changes from background threads is not allowed

I'm trying to use Combine with a view but am getting this error message at runtime:

Publishing changes from background threads is not allowed; make sure to publish values from the main thread (via operators like receive(on:)) on model updates.

I tried adding ".receive(on: RunLoop.main)" before each ".eraseToAnyPublisher()", but that didn't resolve the issue.

Here the code block that I'm assuming is causing the problem:

    func emailAvailable(_ email: String, completion: @escaping (Bool) -> ()) -> () {
        if email != "" {
            print("SignupModel: emailAvailable(): Validating email '" + email + "'...")
            let pattern = try! Regex(pattern: emailRegex)
            if pattern.matches(email) {
                guard let url = URL(string: "https://api.myapi.network/users/email/availability?email=" + email.lowercased()) else { fatalError("emailAvailable(): Missing URL") }
                
                var request = URLRequest(url: url)
                    
                request.setValue(K.apiKey, forHTTPHeaderField: "x-api-key")
                
                let dataTask = URLSession.shared.dataTask(with: request) { (data, response, error) in
                    if let error = error {
                        print("SignupModel: emailAvailable(): Request error: ", error)
                        completion(false)
                    }
                    
                    guard let response = response as? HTTPURLResponse else { return }
                
                    if response.statusCode == 200 {
                        guard let data = data else {
                            print("SignupModel: emailAvailable(): Response contained no data!")
                            return
                        }
                    
                        DispatchQueue.main.async {
                            do {
                                let decodedResp = try JSONDecoder().decode(EmailAvailResponse.self, from: data)
                                if (decodedResp.available) {
                                    print("SignupModel: emailAvailable(): Email available, returning true!")
                                    completion(true)
                                } else {
                                    print("SignupModel: emailAvailable(): Email NOT available, returning false!")
                                    completion(false)
                                }
                            } catch let error {
                                print("SignupModel: emailAvailable(): Error decoding: ", error)
                                completion(false)
                            }
                        }
                    } else {
                        print("SignupModel: emailAvailable(): Response status = \(response.statusCode)")
                        completion(true)
                    }
                }
                dataTask.resume()
            } else {
                print("SignupModel: emailAvailable(): Exiting gracefully because email '" + email + "' is not a valid email!")
                completion(true)
            }
        } else {
            print("SignupModel: emailAvailable(): Exiting because email is nil!")
            completion(true)
        }
    }
    
    lazy var emailValidationAvailable: ValidationPublisher = {
        return $email
            .debounce(for: 0.5, scheduler: RunLoop.main)
            .removeDuplicates()
            .flatMap { email in
                return Future { promise in
                    self.emailAvailable(email) { available in
                    promise(.success(available ? .success : .failure(message: "Email is already registered!")))
                }
            }
        }
        .dropFirst()
        .receive(on: RunLoop.main) // <<—— run on main thread
        .eraseToAnyPublisher()
    }()
     

Anyone know what I'm missing? Thanks in advance!

Aaron