Hey WP,
The only thing that isn't in Dark Mode is the Code Editor. That's by design and I've been lazy and haven't experimented with Code Editor Themes.
Right-click on the editor. In the IDE options select "Editor" > "Display" > "Colors". The second dropdown in the right toolbar is the "Color scheme", select "Twilight" and the editor will be dark as well. Search the forum, there are contributions how to extend the list of color schemes.
Many thanks WP for reminding me where it is. Like I said, I've been lazy and I haven't played around with the themes, but nonetheless I had a vague idea about the general place where I could find it.
But I do appreciate the fact that you suggested Twilight. I always struggle with a selection on these things cuz I'm gonna spend SOOO much time looking at it that if I don't get used to it, it's gonna get my head in

I'm guessing the same is possible under Windows.
No. Windows does not have a real dark mode for the desktop applications, except for a few.
Hummm, I wasn't aware that Windows doesn't have a Dark Theme. I'm aware that some apps have
their own but I was under the impression that Windows already implemented an OS wide Dark Theme.
Maybe it's just me being so comfortable with it under Ubuntu, that I assume, wrongly, that Windows did it first, or had it already.
Oh well, there's another reason for choosing Linux

Cheers,
Gus