Didn’t look at the repo thoroughly, but I can appreciate the work that went into this.
Is there any reason you went this route instead of just using an user-overrides.js file for the standard arkenfox user.js file?
Does the automatic dark theme require enabling any fingerprintable settings (beyond just possobly determining the theme of the OS/browser)?
How are you handling exceptions for sites? I assumed it would be in the user.js file, but didn’t notice anything in particular handling specific URLs differently.