Hello there, @kaidenf55 ...

The request for a dark mode in Canvas is part of a larger theme that you can find here:

Improved UI Controls and Usability - Cleaner or fr... - Instructure Community (canvaslms.com)

If you take a look at the section in that link called "Referenced Ideas", you'll see near the bottom of that list (currently fourth from the bottom) that the following idea is linked:

[Theme Editor] Dark Theme/Dark Mode for Canvas - Instructure Community (canvaslms.com)

So, even though a dark mode does not exist in the Canvas web UI at the moment, maybe it will in the future...who knows.

I know this might not be a direct answer to your question, but I hope it will help in some way.