For those that enjoyed the Lightning Extension Dark Mode it is possible to get it working again. I downloaded an old version of the extension from this URL: https://www.crx4chrome.com/crx/181736 (Version 2.0.7 seems to be the latest version with this feature working.) I then installed it in Chrome using the unpacked extensions feature. You will have to enable developer mode in Chrome first to load unpacked extensions. However, it seems to be working great!