First thing I do when I get a smart appliance is scan it with nmap. This has revealed some interesting Easter eggs, like my Davis instruments air quality sensors having a local REST API.
Doing the usual scan against my GE washer and dryer shows that port 53 is listening. What could that be for? Is there a way I can at least query their status locally or something?
When I got the washer and dryer I was excited about the smart home features because getting an alert when my laundry is done or starting the washer remotely so the clothes are done when I get home are genuinely useful features. However, last time I checked the app none of that was available, so I just have these Trojan horses in my home spying on me with no benefit in exchange. Their app wanted my freaking mailing address when I signed up for their mandatory account, so the features mentioned above are the least they could offer in exchange for my digital soul. But I digress.
My fridge is in a similar situation. It commits the additional cardinal sin of ONLY being controllable via the app, with no on-board temp or filter status indicators whatsoever.
Read the device manuals online. It usually tells you what you need to know
They are doing their absolute best to make that impossible too.
With Bosch, who is normally a very good appliance manufacturer, you have to register your product with them to even be able to download the stripped down user manual.