When we speak about interface design "Dark Mode" is the most desired yet non-priority feature ever.
So it was (or wasn't?) a surprise for me DN had not implemented it yet. Offically or by some enthusiast.
Let me be that person. I've created a custom CSS which can be obtained here:
Installation via well known Stylish extension. I'm not much of a designer so if you find inconsistency or incompleteness of redesign please share your ideas on it.
Works only on desktop version. Also you might be interested in Medium dark redesign: https://userstyles.org/styles/137280/medium-medium-com-dark-grey
Same story about it.
Thank you for attention. :)