It is possible to activate the dark mode in several ways:
Through the settings section:
Access the Blocks plugin > 'Settings';
Find the 'Display Mode' option;
Click on the selector with the sun symbol:
Through the profile selection page:
At the bottom of the screen, click on the selector with the sun symbol:
Through the Profile page:
Click on the sun icon located at the top right of the screen:
To return to light mode, click the selector again, which now shows the moon symbol.