Article seems pretty flawed. Relevance is a vague metric, and the author relies pretty heavily on data related to government site visitation, which seems subject to bias toward certain types of users.
Market share is likely still incredibly low, but Firefox’s relevance should be spiking right now due to Google’s shenanigans with Chromium. The fact that like 90% of revenue for its for-profit wing is from Google is still troubling.
Any alternative views out there?
Few years ago(maybe 10) it was still recommended or even necessary to use IE for a lot of goverment Internet Services here in Germany. The online Zoll handling for example. I think a lot of goverments are not really into accesibility optimization.