Enabling Latin-2?

Please help me,

I would like to enable Latin-2, iso-8859-2,Central European Alphabet respectivelly in username. Its “ěščřžýáíéúů” letters which are used in the Czech republic.

How can I do it?

I guess, I should change something here:

$username = preg_replace (‘|[^a-z\p{Arabic}\p{Cyrillic}0-9 _.\-@]|iu’, ”, $username);
}

Replacing “Arabic” to “Roman”, “Latin-2”, “iso-8859-2” all failed.

Thank you!

https://wordpress.org/plugins/wordpress-special-characters-in-usernames/