I made a real dark user style for cohost. The official dark theme doesn't make the timeline dark, only the background, and it can only be toggled through your system settings, not the website.
You need a user-style extension like Stylus to be able to use it.
- Some posts that use custom css might become illegible. I can't account for all of them but let me know if something is unreadable and I'll see if it's something I can fix.