Rated 4 out of 5 stars
Nice Add-On!! For my private TB it works just perfect, but it seems to me, that it does not work in combination with "Thunderbird Conversations", which is (at least on my work-computer) the most essential Add-On.
If there is a workaround or future Update, which allows to use both TB Conversations and Darko in parallel, it would be great!!
Regarding the "Conversations" - it should work just fine, but only in the native one in the Thunderbird.
I know there is some addon that shows conversations in a better way and I know it doesn't work there. But there is no fix for that - addons in general cannot run inside another addon (to prevent compatibility issues).
The only way to make a dark mode there is to ask the author of that addon to build one.
I'm sorry for the bad news...