They literally mention Vrij Nederland as a source as near enough the first thing in the article: https://en.wikipedia.org/wiki/Vrij_Nederland and https://www.vn.nl/microsoft-ambtenaren-amerikaanse-overheid

Dutchnews.nl is an established media outlet and what a lot of English/non-Dutch speakers use to keep up with Dutch news (which is perhaps surprisingly to Americans, usually written in Dutch)

A bit distrustful, but here you go: https://nos.nl/artikel/2615391-techbedrijven-deelden-namen-n...