I have DietPi with LXQt running on an old netbook, and it looks pretty much like the screenshot, except for the workspaces, bc I donāt use them.
The installation is somewhat old, so maybe they changed the default theme in the meantime?
But you can switch the themes in the system settings.
Maybe you need to log in and out to make the changes working, just a guess.
I also found out that ambience is a default lxqt theme and there is also an apt package for it:
So you can install it with apt install lxqt-themes.
You should see it then in the menu.
Yeah, the āAmbianceā option appeared, and after selecting it and rebooting, the taskbar changed according to the screenshot, but the window decorations still didnātā¦
I found that already too, thereās no āAmbianceā in āQt Styleā but there was one in āLoad Paletteā, and it didnāt change window decorations, only colors inside windows (and not in the same way as shown in the documentation screenshot anyway)ā¦
Ambience is only the LXQt theme, this is indepent from the style of the windows and honestly I donāt know wqhat the name of the color palette etc is. Usually I donāt use a desktop environment on Debian.