inkscape-0.92.4 has the same issue.
The problem is that the API (Programming interface, not Binary interface)
between imagemagick-6 and imagemagick-7 isn't compatible.
And inkscape never was updated to use the API from imagemagick-7.
That's why you are forced to downgrade imagemagick to a version lower than
7 when you want to use imagemagick in inkscape.
If you want to stay with imagemagick >=7 you have two options:
1) entirely disable imagemagick for inkscape, e.g. with "media-gfx/inkscape
-imagemagick" in package.use
2) Use inkscape-1.0.0_beta1 and enable both USE-Flags "imagemagick
graphicsmagick".
That way you will get the imagemagick features through graphicsmagick,
which means imagemagick is not a dependency of inkscape anymore.
Regards
Franz
