Also there's a addon called "decentraleyes" that will cache fonts, amongst other things. It's one of 3 extensions I install in every browser I'm allowed to. The others are uBlock origin and https everywhere. All 3 have good privacy/security/performance benefits with effectively no breakage, in their default configurations.
Decentraleyes is an excellent add-on that improves browsing speed and privacy with no negative side effects. Currently, the only font cached by Decentraleyes is Noto Sans. It also caches Google's Web Font Loader script and many major JavaScript frameworks.
Correction: Decentraleyes doesn't actually cache any fonts. Noto Sans is just used for the add-on interface. Font caching would make an interesting feature if the add-on developer is willing to implement it, especially if it bypasses fingerprinting.
