So, liferea is fine, it has the correct build-dependencies et al.
The problem is that libnm-glib-dev doesn't depend on network-manager-dev as it should, as libnm_glib.pc has:
Requires: NetworkManager >= 0.7.0 glib-2.0 dbus-glib-1
So adding a depends: network-manager-dev (>= 0.7.0) to libnm-glib-dev should fix this.
So, liferea is fine, it has the correct build-dependencies et al.
The problem is that libnm-glib-dev doesn't depend on network-manager-dev as it should, as libnm_glib.pc has:
Requires: NetworkManager >= 0.7.0 glib-2.0 dbus-glib-1
So adding a depends: network-manager-dev (>= 0.7.0) to libnm-glib-dev should fix this.