If I'm reading your correctly you'd like to set FF to the light theme (or any theme) but continue to have dark mode pages? about:config browser.in-content.dark-mode true should do that.
Re:Firefox 72.0
by DyslexicAtheist on Tuesday January 07, 2020 @10:21AM
(#21980712)
I highly recommend dark-reader: https://darkreader.org/
You could also try Firefox Color which provides customizable theming for Firefox, I've had good results with it https://color.firefox.com
Firefox Color is great!! It lets me seamless blend firefox with my doom-themed i3wm and emacs.
[1] https://imgur.com/a/t9tvbQr [2] https://i.imgur.com/GXrTw7C.png [3] https://old.reddit.com/r/unixporn/comments/9f29vr/i3_doom_co...
I agree, and asked around /r/firefox for a solution a while back. Unfortunately without success.
https://reddit.com/r/firefox/comments/dgth9i/automatic_dark_...
Does anyone else get bothered by this? Is there any way around this? I'm not an aesthetics person by any means but this is quite annoying. It's a fantastic browser other than this, I've been a user for as long as I can remember.
I'm sure you can probably modify userChrome and all this and I've not really tried because I'm not THAT bothered by it, but surely there should be a way to set your preferred themes for light & dark?