We now have a alternative dark themes you can use...
To change the theme use the Style option under the General settings of the Settings and Privacy section under Manage Your Account.
To do this, click on your avatar in the top right hand corner to display the control panel.
On desktop's, select 'Manage Your Account' and click on General (as above). The following screen will be shown.
Select the style from the box and hit the submit button.
On mobile, you will need to click on your avatar in the first tab shown, then Manage Your Account...
Make sure to hit the Submit button when done!