Install appdata files to /usr/share/metainfo

$ apt-file search /usr/share/appdata/
fbzx: /usr/share/appdata/fbzx.appdata.xml

...

• Refer: https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#spec-component-location
• Refer: https://appstream.debian.org/sid/contrib/issues/fbzx.html
• Refer: https://appstream.debian.org/sid/contrib/metainfo/fbzx.html