This article is kind of old hat - it's basically been true that Linux is fine as a desktop OS for Grandma since some point circa 2010 +/- a few years. The big requirement is that Grandma just uses web browsers and other basic software from the OSS ecosystem, hardware was relatively compatible to begin with, and somebody does the OS upgrades for her every 3 years.
The real issue is that these kinds of "grandma" users maybe just don't use computers anymore. And the folks that do are joined at the hip to proprietary software like Photoshop or CAD programs or whatever else they care a lot about and don't want to relearn, and also make enough money that the costs are invisible. Or they're business computers and not using what's familiar (Windows) is a support cost.
From this perspective, gaming and specific hobbyists are basically the only feasible audiences for the Linux desktop unless people are very much pressured by software costs, or annoyed by proprietary software (DRM, lockdowns, upgrades, etc.) enough to switch their major activity to an open source option. In which case they awkward situation of "software works better on Linux, but won't try Linux until confirmed they like the not-totally-integrated-and-nice-on-windows-or-mac software running not on Linux."
I do think there ought to be more of a business case for Linux as a business OS as you should get reduced hardware and software and support costs, but there aren't actually a lot of people with the right experience and expertise to run a business off Linux as a desktop OS to begin with and so those savings can't be realized effectively.
That said, as computers get more locked down, I think there will be a bigger drive for power users who influence friends and family to switch.
Any case, my house has had year of the Linux Desktop ongoing since circa 2006.