A student recently shared this Google Chrome extension that makes the Canvas Learning Management System appear in “dark mode”.
Dark mode for Canvas. Staying up late doing homework? Reduce your eye strain and keep your circadian rhythm with this Dark mode for canvas! Canvas dark mode should work for your school, if it does not, contact me and I can update the plugin to include your school's URL! Currently, dark mode for canvas works on any "instructure.com/*" domain.