Would the ADT Hub and ADT/ST offical sensors work without internet or ADT monitoring since they work locally without the cloud? My Dad is retired, does not have internet and was looking to replace his older current alarm that just sounds sirens in the house without notifying anyone when something is tripped…
I’d imagine if it would work i’d have to pair the sensors and set up the system on my home internet before moving it to his house? My last question is if it does work what would be displayed on the ADT Hub where the weather information is?
Yes, you have to have Internet to set it up to begin with. And yes, the specific ADT functions, that is the dual logo sensors or keyfob being used to trigger the ADT panel’s internal siren, Will work without the Internet, but if you are not paying for the monitoring service and the Smartthings cloud is not available you won’t be able to use the mobile app at all and you won’t get any notifications. Just the physical siren going off.
If you just want a simple system that works without the Internet and you don’t need professional monitoring, there are a lot of low-cost security systems available and I would look at one of those first. You’re really not getting any benefit at all from the ADT system in the scenario you described, and it actually has missing pieces. Like notifications. 
Your local Home Depot should have several choices.
I’am looking at the ADT Starter Kit ( I just came over from Iris, recently hooked my ADT Starter Kit and love it) because its simple to use, only sounds alarms in the house(w/o internet or monitoring) and is $99 on Amazon. My Dad is not technically savvy at all. Barely knows the basic functions of using his smartphone so that’s why i was thinking this would be a good match? What other systems similar would you reccomend?