Harmony has the most extensive database, contrary to what URC tells dealers at training. Harmony also introduced the 'Help' button to the remote industry and as much as URC likes to dump on Harmony (the ONLY company they mentioned at the last training session I attended), guess who added a Help button to their remotes.
Yes, they work with audio, video, security DVRs, lights, shades, thermostats, you name it. You can also use a Google Home or Alexa to tell the hub what you want it to do- it's just a matter of adding skills to the Home or Alexa. Harmony can also learn codes, if needed- hub, or not. Their support team is very good, too.
WRT RS-232, I think IP will take over soon enough, so controllers that use 232 will be a dying breed.