OK! I did it!
For those of you using Windows 10 like me (unfortunately, I don't have a choice), it's possible to enable dark mode.
To do this, you need to follow these two steps:
1 - Enable dark mode in Preferences (but this isn't enough because nothing changes)
2 - Enable high contrast mode (and choose the colors you want for each system element)
NOW YOU'RE IN DARK MODE!
Thanks again to the community I help as best I can...