We already have for both nu and nuf https://forum.novelupdates.com/threads/novel-updates-dark-mode.54038/
I second this. For NU, a quick toggle would be nice. However, I have no idea where @Tony would put it without marring the beauty that is NU's homepage.
A quick toggle like https://www.blobtranslations.com/ would be nice. They just recently designed their website.
Wow, @Blob Translations looks a lot like NU, except with pictures, more links, a Discord button, etc. At least NU has NUF, which I like more.