Comment 2 for bug 2026834

The failure happens only on amd64 because that's where arch indep packages are built, and doxygen docs are just that:

d/rules:
build: with_docs=yes
build-arch: with_docs=no
build-indep: with_docs=yes

...
[ "no" = no ] || find build/html/examples/ -type f -iregex .*pdf -exec mat2 --inplace '{}' \;

The build on arm64, for example, only produces these debs:
doxygen-doxyparse_1.9.4-4build1~ppa1_arm64.deb (4.7 MiB)
doxygen-gui_1.9.4-4build1~ppa1_arm64.deb (580.7 KiB)
doxygen_1.9.4-4build1~ppa1_arm64.deb (4.8 MiB)

A working amd64 build, produces these:
doxygen-dbgsym_1.9.4-4_amd64.ddeb (63.1 MiB)
doxygen-doc_1.9.4-4_all.deb (2.0 MiB)
doxygen-doxyparse-dbgsym_1.9.4-4_amd64.ddeb (63.0 MiB)
doxygen-doxyparse_1.9.4-4_amd64.deb (4.7 MiB)
doxygen-gui-dbgsym_1.9.4-4_amd64.ddeb (2.7 MiB)
doxygen-gui_1.9.4-4_amd64.deb (271.6 KiB)
doxygen-latex_1.9.4-4_all.deb (4.2 KiB)
doxygen_1.9.4-4_amd64.deb (4.7 MiB)