Strictly through built–in settings, sure. There are plenty of extensions that will let you override fonts in a more granular way [0] or even override styles alt

Strictly through built–in settings, sure. There are plenty of extensions that will let you override fonts in a more granular way [0] or even override styles altogether [1]. [0] https://addons.mozilla.org/en-US/firefox/search/?q=change+font https://addons.mozilla.org/en-US/firefox/search/?q=change+fo... [1] https://addons.mozilla.org/en-US/firefox/search/?q=style https://addons.mozilla.org/en-US/firefox/search/?q=style