https://www.mozilla.org/en-US/firefox/android/68.0.2/releasenotes/

68.0.2 Firefox for Android Release August 14, 2019

Fixed
Allow fonts to be loaded via file:// URLs when opening a page locally (bug 1565942)

https://ftp.mozilla.org/pub/mobile/releases/68.0.2/
68.0.2来てる。