Last question first - there is lynx for a text browser. Personally never used it but back in the day of NNTP, there were a lot of network guys that swore by it and emacs. For colors, have you gone to settings>general>contrast control? You could play around there to see what you can change. By dark mode you mean the settings a little higher on that general page, correct? I think the only way to change that would be to look at the themes available outside Firefox through tools on the menu or the link there in general settings under the mode settings. What is your os? You may be able to play around with some color palettes in system settings. You want to pay attention to what firefox does when you change system colors.

First of all, thanks for the reply!

Yes that is exactly what I mean by dark mode. Themes and colour palettes were previously how I configured those higher portions of the interface - with todays update they no longer apply, and those sections seem to be locked to white.

I will try Lynx for the time being. Thanks again!

System:

5.15.0-144-generic #157-Ubuntu SMP Mon Jun 16 07:33:10 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux

Firefox's "System" or "Default" theme isn't picking up the signal from Cinnamon for dark mode. Apparently if you go to your system settings and switch to Light and back to Dark, Firefox will get the message, but obviously that is inconvenient because it only lasts until you quit Firefox.

You may want to use Firefox's built-in dark theme instead of the "System" theme until this is sorted out. See: Use themes to change the look of Firefox.