Anything with an ARM Mali family GPU, same as you'd find for the question "where are Nvidia drivers used" as being "anywhere an Nvidia GPU is used". There isn't a premade list of certain people/companies who might ever used a certain brand GPU in their products, it's "just about anywhere". That can be anything including phones, tablets, mini PCs, laptops, SBCs, TV boxes, VR headsets, and so on - it's not limited to use in a specific product/manufacturer/type of device only.
If you're looking for something hackable to play with the Mali driver options on yourself, Chromebooks or SBCs (like the one in the article) are usually the easiest bet and where the development is done vs the more fixed-by-manufacturer type devices like the typical phone where you get what they decide to package (which may or may not be the particular open driver you're looking to see used).
Hmm, not really. As mentioned above, anything including phones, tablets, mini PCs, laptops, SBCs, TV boxes, VR headsets, and so on. Chromebooks and TVs would just be 2 examples of these types of devices.
As a solid example, the screenshots from the article are not taken from a Chromebook or TV :).
If you're looking for something hackable to play with the Mali driver options on yourself, Chromebooks or SBCs (like the one in the article) are usually the easiest bet and where the development is done vs the more fixed-by-manufacturer type devices like the typical phone where you get what they decide to package (which may or may not be the particular open driver you're looking to see used).