Dear All,
I hope you are doing great, we have a question in regards to a project we are doing in our local home country. We are thinking about hosting the platform locally on-premises to manage a 15,000 gateway with various sensors / devices through the mobile app where no connection will be going outside of the country, is that even possible or smarthings allows only public cloud setup?
Smartthings is still primarily a cloud-based system, so not possible. 
You can look into Hubitat or Insteon and see if they would meet your needs.
Also apple’s HomeKit runs locally except for voice control.
Thanks for your reply & really appreciated. What about Fibaro, does it run locally?
I’m sorry, I don’t know if their hub runs locally or not. you would need to check with them.
@amiralaa, you would probably need a white label provider. Look at https://yourcockpit.biz/ or there is another company, Develco, which provides white label equipment. I am not sure that do they provide gateways and backend as well, but I will tag the contact here.
@Mohammed_Seifu_kemal, are you dealing with this kind of business models as well as in the OP?
yes, our flagship product is infact a gateway, the squid.Link gateway and an open wireless platform that supports various technologies, please see https://www.develcoproducts.com/products/gateways/squidlink-gateway/