DiMarco

As a moderator, I raised this. We're due a forum software update soon, and we're hoping that a dark theme will be implemented as part of that.
More details soon hopefully.

As a temporary expedient - ( and using Firefox - can't speak for the other browsers ) go to -
Menu - Settings  ;  scroll down to "Language and Appearance" and under Fonts & Colours, select Colours.  On the Background option, click the rectangle and the colour palette appears. Select a tone that suits you and lighten it with the side strip. Save your choice.

Under "override the colours" select always.

It's far from infallible, but it works on Basschat and the BBC. If you see some features or text disappearing elsewhere, then you'll have to cancel the setting.

OR
With Windows 10, Go to Settings - System - display - & turn on the night light slider. If you click on Nite-Light Settings there are more options.

Balcro's idea is good, I always have the 'Night Light' on Win10 turned on with the 'blue' dialled down to 66%.  Much kinder on the eyes.