It's microwaves, like in one's kitchen. Most aren't “smart”, but the smart ones are usually ARM-based Linux systems (sometimes Android).

FM11VABK does not require an Internet connection or a mobile app

An innovation, solely for how it is a rare example of “safe” smart electronica. Plus, it appears to be a good product. Whether it’s possible to do anything else with the Rockchip is unknown.

https://www.cnx-software.com/2021/05/07/linux-microwave-oven-rockchip-rk3308-voice-control/

It runs Android under the hood, so I was able to push a Doom APK to it using ADB

This thing is discontinued and long gone now, so finding one will likely be a stretch. Runs Android, quite clearly, and can also access a web browser and such.

https://www.reddit.com/r/itrunsdoom/comments/cuoymo/doom_on_a_microwave/

https://www.reddit.com/r/itrunsdoom/comments/cuoymo/doom_on_a_microwave/exxsnwf/