Interesting article where ~35k devices from 45 manufacturers have vulnerabilities
Advice is probably not as easy to implement as this in real life:
Forescout recommends that you immediately stop the direct connection of devices to the Internet, to use VPNs or segmented networks, and to ensure prompt firmware updates. Otherwise, tens of thousands of systems around the world will remain a potential entry point for attackers.
I still don’t understand why is it so essential to connect everything to the internet
It’s just “easier” to connect devices to the internet and provide the end user with an (unmaintained, insecure) app on their phone to see it’s doing something.
But, I seriously doubt I could find any updated firmware for my inverter (which is not connected to the internet)
In this case I guess mostly to collect data about insulation for each region. One time my provider called my home to tell the panel was dirty and needed cleaning to recover the efficiency