[Koha] Encoding and Character Sets in Koha

When cataloguing books with non-english characters, I see well saved strings at database (from OS console), but Koha web interface is not showing those unicode characters as expected. MariaDB works with character set utf8mb4 Apache works with charset UTF-8 All Koha database tables have collarion utf8_unicode_ci Koha HTML output is UTF-8 encoded and includes Content-Type... charset=utf-8 Using Koha 17.11.06-1 on Debian 9. I don't find Koha's system preferences about this. What can I review? Thanks.