/usr/ is in thunderbird-locale-cs 1:38.6.0+build1-0ubuntu1.
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..
/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/cs/
/usr/lib/thunderbird/distribution/searchplugins/locale/cs/heureka-cz.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/cs/twitter.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/cs/wikipedia-cz.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/cs/slunecnice-cz.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/cs/mapy-cz.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/cs/seznam-cz.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/cs/bing.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/cs/google.xml
/usr/lib/thunderbird-addons/
/usr/lib/thunderbird-addons/extensions/
/usr/lib/thunderbird-addons/extensions/langpack-cs@thunderbird.mozilla.org.xpi
/usr/share/
/usr/share/doc/
/usr/share/doc/thunderbird-locale-cs/
/usr/share/doc/thunderbird-locale-cs/copyright
/usr/share/doc/thunderbird-locale-cs/changelog.Debian.gz