okular "cannot find latex executable"

[inkbottle <inkbottle007@gmail.com>]

Okular has a functionality allowing to insert LaTeX code inside inline notes 
by simply putting it between `$$`, like this: $$\sqrt 2$$.

Okular suggests texlive-binaries as dependencies.

The how to do it is described here:
https://docs.kde.org/trunk5/en/kdegraphics/okular/annotations.html

Basically you write your inline note, then you double click it in order to 
edit it, and there, there is a messages saying to click it in order to render 
the Latex code.

But then, what happens for me, even though I've installed the "suggested" 
texlive-binaries, and rebooted in between, is that I get a message saying 
"cannot find latex executable".

I've probably missed something. The functionality is suppose to be here since 
2012. It is the first time I try it. Just discovered it as a matter of fact.

Chris