I'm using the Dark Theme of the Debian 9 with KDE Plasma 5.8.6, but when I open the Libre Office, this is what I see: I think this gradient is very ugly, so I want to change for a solid color, or for another theme that matches with the system.
I found a way to do this look better.
First, I had to install libreoffice-breeze-icons at the Libre Office and set this as the icon theme on
Tools > Options > LibreOffice > View > Icon style.
Then, I needed go to
Tools > LibreOffice > Options > Accessibility and check the box Automatically detect high contrast mode of operating system.