With the introduction of the Next Experience UI (Polaris) there was finally the option to choose a Dark theme, but if you cannot or will not use the Polaris UI then you are forced to use the default white theme.
In that regards I decided to create an equivalent Dark theme for the Platform UI. Inspired by the VS Code dark theme and a similar post on the community, I created a theme to fill the gap and make it easier for working those late hours in the evening or at night 🙈
The theme can be found here and it is an userstyle that can be used together with a browser extensions like Stylus or Stylish.
The theme uses CSS variables, so with a few changes you can make your own variant:
To be noted that this theme is not compatible with the Polaris UI and it can effect UI pages since there is no easy way to add exceptions for so many pages.
Hope this proves useful!
Additional screenshots:
