These custom fonts that people use are so unnecessary... Just let me use my browsers' default!
https://edwardtufte.github.io/et-book/
Modern browsers also have preferences to switch off web fonts.
It looks like ET-Tufte has already considered and tried to mitigate this downside. [2]
[1]: https://web.dev/optimize-webfont-loading/
[2]: https://et-jekyll.netlify.app/et-jekyll-theme/#performance
[0]https://twitter.com/typographica/status/1395769805542547461?...
Just disable fonts in the browser settings then.