No — Subtil isn’t listed as a free font. The link at the top of this page goes to the source, where you can check licence options.
At first glance, Subtil Grotesk may look just as your next Helvetica-class sanserif. At hearing "Helvetica", many of us might think ‘Oh no, this is much different!’ Yes, Subtil is a good sample of a world where the dominance of the serious post Great-war Grotesque, such as Monotype Grotesque No.1/10, Helvetica, Folio, Akzidenz, News Gothic, Venus and more, persuaded type designers to add many pastiches to that class.
A1 features 1 website using Subtil. It leans towards Fun, Typographic, and Shapes design styles, and it’s most often built with Shopify.