You can query the information about individual devices that are connected to your ST account in a couple of different ways, but there is no “device database“ as it sounds like you’re describing it.
SmartThings provides a set of stock edge drivers on each hub, but they don’t cover all possible devices and it’s the radios inside the hub that allow the communication with many devices, not just the edge driver definitions. So even if you got all the stock edge drivers, say from GitHub, it wouldn’t enable your standalone raspberry pi to talk to those devices.
You could design an MQTT broker for your raspberry pi so that it acted as the front end to your SmartThings account and let a SmartThings/Aeotec hub do all of the actual communication. That’s similar to how the various third-party dashboard apps like sharptools and action tiles work (although they don’t use MQTT), but you would still have to have and maintain a SmartThings account to make it all work.
So it depends on what your goals are. If you just want a more robust rules engine and a custom UI, that’s very doable if you have the tech skills. See, for example, the following project report:
Unleash the Power of SmartThings with Advanced Automations Using Node-Red
But if you’re trying to substitute for the transport level, you will have to provide your own radios and whatever information you get from SmartThings just isn’t going to help you very much except give you some ideas of what to research. 