I asked about Dark Mode for the CCF website long ago and found that it was too costly to change the CCF code over to enable it.
I just found an extension for Edge called 'Dark Reader' that switches websites automatically. I have problems reading the bright background pages and sometimes the contrast isn't what I need. Dark Reader solves all of the problems I've been having and is customizable!
You can set it to handle each website differently if you wish. This will make a huge difference in most website's readability for me and I hope will give me some relief from the headaches I've been having after reading the CCF for 20 hours each day.
It's FREE to install and use, but the developer will take donations.
Give it a try if you like or NEED to use dark mode when surfing the web as I do.
(No, I'm not the developer nor do I get anything from them. I'm just really pleased with this extension!)