Given the recent \"encouragement\" by Facebook to migrate to a separate messenger app, and as a followup to the {very informative!} answer to the question on URL/URI schemes
With current version Facebook on android automatically ask user to open the app or open in chrome when you use their domain www.messenger.com It's better to just redirect user to this url and let facebook handle it
https://www.messenger.com/t/{username-or-page-name-here}
Intent intent;
intent = new Intent(Intent.ACTION_VIEW, Uri.parse("https://www.messenger.com/t/{username-or-page-name-here}"));
startActivity(intent);