Anyone here knows, why the hell the installation of xpdf (in devuan)
needs to deinstall lxde and lxde-desktop-tasks?

I do not understand the reason why (in slackware for example there did
not exist this problem). May be that's an inherited dependency problem
(?)

Me, as a simple user, i would like to suggest, that capable people step
by step might have a look in all this dependency spiderweb (with the
obvious target to cut all of it which not really is needed).

Please do not take me wrong, i'm far from being able to judge this, but
often it is my impression, in debian there way more dependencies
excluding reasonable options than really necessary.

Cheers