JavaScript is here to stay, web browsers are here to stay, they can make GUIs that are durable.
I find it comical that X was the chosen target in this article, as it will most certainly be more than crufty in 5, let alone 20 years from now.
If you integrate with an html+js viewer, do you link it into your binary? If so, what are its dependencies and will they be around? If not, will you still be able to use the same viewer in 5-20 years or will it have some breaking change that requires additional work?
Worst case, you run VcXsrv in Wine, because win32+wine is the future proof platform; but if we're all running Wayland then, Xwayland should work, and I'd bet money if there's a replacement for Wayland in the next 5-20 years, it will have an available X server even if it can't integrate with Wayland clients.
And while on paper a web application built 20 years ago still works today as it was, the same can't be said about the technology used to develop and build these; there's a ridiculous amount of churn in the libraries and frameworks, to the point where you have to set up your github actions or whatever to frequently keep your stuff up to date, because if you run more than six months behind, any updates will break your carefully balanced setup.
Of course, that's a choice. Ultimately there's no real need to use Typescript, a framework, or a collection of libraries, and if you do choose them, there's the huge complex but fragile ones like Angular and React and their ecosystems, or smaller ones leveraging modern web tech developments or solving only a single problem. (I'm aware React was intended that way originally but in practice it's a whole ecosystem you're pulling into your application)
Yet, most would consider the term to refer to purpose-build interfaces, rather than those build upon the 'GUI' of a web-browser - which has it's own idiosyncrasies.