Mariadb json store with unicode \u sequences
\u0395 is just 6 characters to MariaDB.  Searching for the 5-character &quot;word&quot; u0395 would succeed.
You need to change the JSON strings to have characters, not unicode codepoint encoding.
In PHP, I would consider write a 1-time script to bring in each line, decode it, and write it back out.
Meanwhile, the writing should be changed to
json_encode($stuff, JSON_UNESCAPED_UNICODE)

(or the equivalent in your app's language).
IntlChar::chr may be part of the solution.
Or:  $utf8string = html_entity_decode(preg_replace(&quot;/U\+([0-9A-F]{4})/&quot;, &quot;&amp;#x\\1;&quot;, $string), ENT_NOQUOTES, 'UTF-8');
Or:  https://stackoverflow.com/questions/6058394/unicode-character-in-php-string
Or:  https://stackoverflow.com/questions/2934563/how-to-decode-unicode-escape-sequences-like-u00ed-to-proper-utf-8-encoded-cha