Comment 3 for bug 1705653

The github commit you pointed to already exists in the Ubuntu package, but org.valapanel.appmenu-gtk-module.gschema.xml isn't installed.

That looks like an embedded code copy of unity-gtk-module which isn't allowed according to Debian Policy 4.13, at least as long as unity-gtk-module is still in Ubuntu.

https://www.debian.org/doc/debian-policy/ch-source.html#s-embeddedfiles

I'll let flexiondotorg look into all this more.