Sergey Biryukov

Allows to create users with usernames containing Cyrillic characters.

Allow Cyrillic Usernames

Allows users to register with Cyrillic usernames.

dlesendric

Cyrillic to latin only transform _rs_RS files, don’t use this plugin if you want to use both translation, for this you have different types of plugins. 
Use this plugin only with Serbian language, because i’t won’t work with others. 
Transform any cyrillic translation of wordpress language file. It can transform themes, admin’s and woocommerce translation files.

Cyrillic To Latin

Cyrillic To Latin is a plugin for transforming Serbian Cyrillic .po files into Latin .po files.

Allow Cyrillic Usernames vs Cyrillic To Latin