It turns out, that changing dh_strip --no-automatic-dbgsym -Xvmlinux to dh_strip --no-automatic-dbgsym -Xvmlinux -Xvmlinuz in debian/rules.real fixes the build.
I added some tracing code and this shows that in former compat level 9, the strip command is never executed on the vmlinuz file, while with compat level 12, strip is now executed like this and thus fails: strip --remove-section=.comment --remove-section=.note --strip-unneeded debian/linux-image-5.6.0-1-parisc64/boot/vmlinuz-5.6.0-1-parisc64 strip: debian/linux-image-5.6.0-1-parisc64/boot/vmlinuz-5.6.0-1-parisc64: file format not recognized dh_strip: error: strip --remove-section=.comment --remove-section=.note --strip-unneeded debian/linux-image-5.6.0-1-parisc64/boot/vmlinuz-5.6.0-1-parisc64 returned exit code 1 Any chance we can add "-Xvmlinuz" to the dh_strip command in rules.real?