Firefox 62 ships today, bringing with it some real CSS goodness. For one: float shapes! Which means now, mainline Firefox users will see the text flow past the blender in “Handiwork” the same way Chrome users have for a long time now.
But an even bigger addition is support for variable fonts. The ability to have one font file that mathematically describes variants on the base face means that all kinds of fine-grained typography is possible with far less bandwidth overhead and a major reduction in page weight.
However: bear in mind that like Safari, but unlike Chrome, Firefox’s variable-font support is dependent on the operating system on which is runs. If you have Windows 10, or Max OS X 10.13, then you have variable font support in Firefox and Safari. Earlier versions of those operating systems don’t support variable fonts, and so Safari and Firefox don’t either. Chrome rolls its own variable-font support, so it can extend support backwards in the OS timeline.
(I don’t know how things stand in the Linux world. Hopefully someone can clear things up in the comments!)
I say this not to chastise Firefox (nor Safari), because I tend to think leaning on the OS for this sort of thing is reasonable. I feel the same way about form elements like
<select> dropdowns, to be clear, which I know likely places me in the minority. The point here is to give you a heads-up: if you get reports that a font isn’t doing the variable thing you styled, but it’s working fine for you, keep “check their operating system version” on your list of diagnostic tests.