Cannot understand if Alexa-only devices can be used by HA

Hello, I’m pretty new to the domotic world and I’m reading a lot about HA and everything around it. I’ve read a lot about Alexa integration on HA (Nabu Casa or haaska) and I’m sure that I can control HA devices with my voice using Alexa, but… I’m confused on the opposite way.

I have a couple of devices that “works with Alexa” (only) and I’d want to being able to control them on my HA installation. Example: I want control my thermostats within HA to being able to use some kind of logic.

I read about the Proactive Events, but I’m not sure that is what I’m searching for…

Sorry for the stupid questions but I cannot find a clear answer and I’m going crazy about it :slight_smile: