/usr/lib/thunderbird/distribution/ is in thunderbird-locale-sk 1:38.6.0+build1-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/thunderbird/distribution/searchplugins/
/usr/lib/thunderbird/distribution/searchplugins/locale/
/usr/lib/thunderbird/distribution/searchplugins/locale/sk/
/usr/lib/thunderbird/distribution/searchplugins/locale/sk/atlas-sk.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/sk/azet-sk.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/sk/bing.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/sk/eBay.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/sk/google.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/sk/slovnik-sk.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/sk/wikipedia-sk.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/sk/zoznam-sk.xml