glareless by Jaime Silvela

Many (most?) web pages that don't use dark mode, use the default background of full white for text areas. Notably, most mainstream news sites.

This is uncomfortable for reading on prolonged sessions. You're forced to look at something bright intently, because you're reading.
In addition, full black text on full white background is very high contrast, much higher than ink on paper.

This extension watches for text areas, and if the background is brighter than a threshold value (configurable) it applies a more muted background color (also configurable).