Dark Theme for Yandex™ by Balvin

This extension brings dark them (night mode) to Yandex homepage and Yandex search results. The extension is based on the inversion filter but offers custom user CSS code injection to fine-tune the theme to your needs. This extension also supports schedule on and off which allows the user to turn the dark them only during custom night time.

Note: If your browser has "allow access to search page results" option for extensions on the extensions manager, then you will need to accept it for the extension to be able to inject its CSS code.
Note: You can simply toggle the dark theme on and off from the toolbar button.