It’s possible to do this with any smart plug that works with smartthings and any smoke sensor that works with smartthings, but the question is the reliability.
Smartthings themselves say in their product usage guidelines that you should not rely on it for anything that might impact health or safety.
So if you want to use it just as a convenience feature, that’s fine, just prepare for the idea that it might fail every once in a while.
If you find a Wi-Fi plug that works for your microwave specifications and that works with smartthings and that does not require a hub and you find a smoke sensor that works with smartthings that does not require a hub, then you won’t require a smartthings/Aeotec hub to do this. You’ll just need the smart plug and the smoke detector.
I personally use Meross brand WiFi plugs: They are well engineered, have good safety certifications, are available in both the US and the UK, and work well with smartthings. But I haven’t looked at the specifications to see if there is one that would work with the microwave, and again, different microwaves have different specifications. so it all comes down to the first rule of home automation: the model number matters.
Also, what country are you in? The device selection does vary.