I know that the dark mode setting is disabled by Resist Fingerprinting. I am not using that, I am using the Dark Reader extension. The extension still doesn’t work, but it works on Firefox.
Other extensions I have installed: Ublock Origin, Decentraleyes, Skip Redirect, Onetab, Old Reddit Redirect
Librewolf version: 124.0.1-1
Tested here with LibreWolf Flatpak where I made no changes with about:config. Works fine. Disable a few other extensions and see what gives ?