this package seems to have new commits in its VCS but has
not yet updated debian/changelog. You should consider updating
the Debian changelog and uploading this new version into the archive.
Here are the relevant commit logs:
Author: Adrian Bunk <email@example.com>
Date: Mon Aug 13 18:40:42 2018 +0300
python-plplot-qt lost its generated python dependencies
Author: Michael Cree <firstname.lastname@example.org>
Date: Wed Jun 20 21:56:18 2018 +1200
Don't misdetect compiler on Alpha as not supporting NaN
Author: Sergei Golovan <email@example.com>
Date: Sun Mar 18 21:00:53 2018 +0300
Switch to Itcl/Itk 4
I'm planning to switch the iwidgets4 package from Itcl/Itk 3 to Itcl/Itk 4.
And I'd like to do that before the buster's release. Currently, plplot depends
on iwidgets4 and itcl3, itk3 (actualy, if you look at the build log  you'll
find that itcl stuff is disabled, but anyway, it's probably the subject of
Upstream seems to have support for Itcl/Itk 4 (there's one option in
tcl-related.cmake to switch on, thought I also had to change the Itcl
headers search path). The proposed changes are in the attached patch.
So could you test if the plplot-tcl is indeed working with Itcl/Itk 4?
You could upload this package into experimental, iwidgets4 built
against Itcl/Itk 4 is already there.