Hi,
Thanks for your rating. It's great to hear that you like the add-on. 😀

If I understand you correctly, you seem to have an issue with forcing the dark mode for static local files.
As far as I know and what I would say without having a deeper look into it, this should theoretically work.

Thus, to troubleshoot this issue, we'd need more information about your system (i.e. what OS and what Firefox version do you use?). It would be glad if you could open an issue on https://github.com/rugk/website-dark-mode-switcher and fill out the details there, so we can fix this problem in the next release.

Any help is clearly always appreciated.

Best regards,
rugk