Just a hypothesis, in case it helps…
It looks like the generated “SD light theme” CSS at https://sea3.discourse-cdn.com/straightdope/stylesheets/desktop_theme_15_c2be2adfc9b9eefa0ac79b1f4d36de9cf5f05692.css is broken due to an SCSS compiler error. (The generated dark theme CSS still works.)
Putting a few things together, it looks like:
- Line 42’s
background: color.adjust($quaternary, $lightness: -10%);seems to require an explicit module import of@use 'sass:color'; - This used to be implicitly available, but not after Dart Sass 1.79.0, and Discourse recently upgraded their SASS and disabled the deprecation warning because it was too noisy. This probably killed our custom theme.
- The fix for our custom theme is to either explicitly import that module (if possible) or rewrite it in more recent SCSS styling for Discourse, e.g. Use Discourse Core Variables in your Theme - Developer Guides - Discourse Meta and Update themes and plugins to support automatic dark mode - Developer Guides - Discourse Meta.
- Maybe something like
background-color: var(--quaternary); filter: brightness(90%);would work? - Since we’re a hosted customer, Discourse (or rather the company behind them) might be willing to help at Discourse moved to Dart Sass - Announcements - Discourse Meta