A more reliable approach, though requiring a reload, is to block web fonts in uBlock Origin (which you’re using, right?)—there’s a button for the purpose. You

A more reliable approach, though requiring a reload, is to block web fonts in uBlock Origin (which you’re using, right?)—there’s a button for the purpose. You can also just turn font choice off altogether, so that you just get your chosen serif/sans-serif/monospace/whatever fonts. In Firefox, it’s Settings → Fonts → Advanced → untick Allow pages to choose their own fonts, instead of your selections above. I started doing that a couple of years ago as an experiment and have never gone back: it makes the web so much better with minimal and typically unimportant breakage.