I know there was a discussion a while back about running AppArmor and Firejail together. I believe it was decided that there may be some coding conflicts for the two. I don’t know when this was added but on the Firejail ArchWiki section 3.3 on the page it describes running both:
https://wiki.archlinux.org/index.php/firejail#Enable_AppArmor_support
I know Arch is not Debian but is that coding apply-able or desirable for Whonix?