/usr/ is in thunderbird-locale-ca 1:38.6.0+build1-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/
/usr/lib/thunderbird/
/usr/lib/thunderbird/distribution/
/usr/lib/thunderbird/distribution/searchplugins/
/usr/lib/thunderbird/distribution/searchplugins/locale/
/usr/lib/thunderbird/distribution/searchplugins/locale/ca/
/usr/lib/thunderbird/distribution/searchplugins/locale/ca/wikipedia-ca.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/ca/diec2.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/ca/bing.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/ca/huubs.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/ca/llibres.xml
/usr/lib/thunderbird-addons/
/usr/lib/thunderbird-addons/extensions/
/usr/lib/thunderbird-addons/extensions/langpack-ca@thunderbird.mozilla.org.xpi
/usr/share/
/usr/share/doc/
/usr/share/doc/thunderbird-locale-ca/
/usr/share/doc/thunderbird-locale-ca/copyright
/usr/share/doc/thunderbird-locale-ca/changelog.Debian.gz