... This plugin sets the dark mode on websites ...

Found a first solution with the additional installed addon 'automaticDark - Time-Based Theme Changer' of simonkhzhang. In settings of this addon set only 'Change themes based on the system theme' and both! 'Daytime theme: and Nighttime theme:' to light not to dark (german means hell anstelle dunkel). Hope this works for you. Kind regards, Gerald