can we open download folder via. intent?

You can show the recent downloads activity with the following Intent

startActivity(new Intent(DownloadManager.ACTION_VIEW_DOWNLOADS));

Available since API 9

Samsung solution:

public static void openDownloads(@NonNull Activity activity) {
    if (isSamsung()) {
        Intent intent = activity.getPackageManager()
                .getLaunchIntentForPackage("com.sec.android.app.myfiles");
        intent.setAction("samsung.myfiles.intent.action.LAUNCH_MY_FILES");
        intent.putExtra("samsung.myfiles.intent.extra.START_PATH", 
                getDownloadsFile().getPath());
        activity.startActivity(intent);
    }
    else activity.startActivity(new Intent(DownloadManager.ACTION_VIEW_DOWNLOADS));
}

public static boolean isSamsung() {
    String manufacturer = Build.MANUFACTURER;
    if (manufacturer != null) return manufacturer.toLowerCase().equals("samsung");
    return false;
}

public static File getDownloadsFile() {
    return Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
}

Found by decompiling the Samsung My Files app dex and seeing how the MainActivity deals with intents.

public static final String MYFILES_NOTIFICATION_LAUNCH_INTENT_NAME = "samsung.myfiles.intent.action.LAUNCH_MY_FILES";
public static final String NOTIFICATION_START_PATH = "samsung.myfiles.intent.extra.START_PATH";
public static final String START_PATH = "FOLDERPATH";

if (Constant.MYFILES_NOTIFICATION_LAUNCH_INTENT_NAME.equals(intent.getAction())) {
                String startNotificationPath = intent.getStringExtra(Constant.NOTIFICATION_START_PATH);
                if (startNotificationPath != null) {
                    Bundle newArgument = new Bundle();
                    newArgument.putString(Constant.START_PATH, startNotificationPath);
                    if (new File(startNotificationPath).exists()) {
                        startBrowser(513, newArgument);
                    }
                }
                intent.removeExtra(Constant.NOTIFICATION_START_PATH);
            }