I broke the landing page's background in D6003 by adding a CSS selector that applied globally to html and body.
Turns out doing it right is a bit harder. In order to avoid needing dynamic imports, I needed to stop relying on html and body for styling, as they appear above #react-root. To make that happen, I had to move the background styling to inner divs, which required moving some CSS attributes around to get everything to look right.
This solves https://linear.app/comm/issue/ENG-2535/landing-page-background-is-messed-up