I currently have these files:
-rw-r--r--  1 mattia mattia  1137384 Oct  4 21:58 inkscape_1.0~beta1+ds.orig-extensions.tar.xz
-rw-r--r--  1 mattia mattia 31096177 Sep 17 12:17 inkscape_1.0~beta1+ds.orig.tar.bz2
-rw-r--r--  1 mattia mattia      195 Sep 22 17:11 inkscape_1.0~beta1+ds.orig.tar.bz2.asc
So I ran this:
mattia@warren ~/devel/debian/inkscape/inkscape (git)-[experimental] % gbp import-orig --no-pristine-tar --component=extensions ../inkscape_1.0\~beta1+ds.orig.tar.bz2
What is the upstream version? [1.0~beta1+ds]
gbp:error: Can not find component tarball ../inkscape_1.0~beta1+ds.orig-extensions.tar.bz2

That is despite that if I unpack the stuff by myself, `dpkg-source` is
perefectly able to deal with multiple tarballs compressed differently.

Please teach gbp to deal with that :)