Unity - How to open Samsung Internet App from my Unity App

Virtual keyboard and in-app browser support aren't available yet. But you can send an intent to a web browser as described here. See the ACTION_VIEW intent:

Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(<your_url_string>));
        public static final String SAMSUNG_INTERNET_PACKAGE_NAME = "com.sec.android.app.sbrowser";
        // Extra used to match the session.
        private static final String EXTRA_SESSION = "android.support.customtabs.extra.SESSION";
        Bundle extras = new Bundle;
        extras.putBinder(EXTRA_SESSION, sessionICustomTabsCallback.asBinder());
        intent.putExtras(extras);
        intent.setData(url);
        intent.setPackage(SAMSUNG_INTERNET_PACKAGE_NAME );
        context.startActivity(intent);

If the user doesn't have the Samsung internet browser installed (which is not uncommon), this will fail. You may want to prompt the user to install it or use a generic ACTION_VIEW intent like the following:

try {
    Intent myIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(download_link));
    startActivity(myIntent);
} catch (ActivityNotFoundException e) {
    Toast.makeText(this, "No application can handle this request."
        + " Please install a webbrowser",  Toast.LENGTH_LONG).show();
    e.printStackTrace();
}