https://bugzilla.redhat.com/show_bug.cgi?id=1409348
--- Comment #3 from Nicolas Mailhot nicolas.mailhot@laposte.net --- It's almost certainly a bug in the Firefox font handling code
Fedora uses a lot of substitution rules in fontconfig, in particular for Droid
They've been vetted by the fontconfig upstream maintainer before deployment and haven't changed for years (and the open sans package didn't follow those rules last time I checked leading to problems)
However, because they are advanced and complex, they've tripped implementation bugs in apps that do stuff with fonts in the past (for example QT) when upstream didn't implement properly all the fontconfig substitution logic. IIRC Suse and Ubuntu do not push fontconfig as hard as Fedora, so they won't hit the same application bugs.