NSURLSessionDataTask does not work on macOS, "A server with the specified hostname could not be found."

Why does dataTaskWithURL work on iOS, but not on macOS?

The error message is:

Client-Error: A server with the specified hostname could not be found.

My routine is as follows:

- (void)loadHTML {
    NSString *urlString = @"https://morph.zone/modules/newbb_plus/viewtopic.php?topic_id=12630&forum=10";
    NSURL *url = [NSURL URLWithString:urlString];
    NSURLSessionDataTask *downloadTask = [[NSURLSession sharedSession] dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
        if (error != nil) {
            NSLog(@"Client-Error:%@",error.localizedDescription);
        }
        else {
            NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
            if (httpResponse.statusCode < 200 || httpResponse.statusCode > 299) {
                NSLog(@"Server-Error:%ld",httpResponse.statusCode);
            }
            else {
                NSLog(@"Data downloaded");
            }
        }
    }];
    [downloadTask resume];
}

For macOS targets, you must explicitly enable “Outbound Connections (Client)” on the “Capabilities” tab:

Until you do that, all outbound connections will fail with NSURLErrorCannotFindHost error.