Firefox View Doesn’t Feel Like a Feature, Mozilla. It Feels Like a Nag
The unexpected addition (that masquerade as a pinned tab) is for new feature (in testing) called Firefox View. This is a dashboard-style overview showing your 3 most recently closed tabs, plus sections to “pickup” tabs you’re gawking at on your other devices, and promotion for more limited-edition “colorways” (no idea, lol).
But… I need to digress ...
As a Linux user I take for granted how omnipresent Firefox is. In FOSS-world, this browser is still a big deal; I can pretty much count on a lone hand the number of major Linux distros that don’t ship it as their default browser. Also: it’s very widely used — Firefox is the browser zeitgeist, innit.