You can also select your own fonts and prevent pages from overriding them. Preferences → Fonts → Advanced → untick “Allow pages to choose their own fonts, instead of your selections above”. I did this a few months ago, and I’ve seen no breakage outside icon fonts, and apparently icon fonts are deader than I thought they were—DuckDuckGo has a few unimportant ones, and beyond that the only ones I’ve seen are Google’s Material Icons font, which uses a ligation technique that’s supposed to make things better but actually makes them vastly worse.

Over all, I’m much pleased by the results of forcing Equity/Concourse/Triplicate.