When compiling LESS to CSS, the Cyrillic alphabet turns into krakozyabry, how to fix it?

Question

css

LESS: ::before {content: "ы";}
or
::before {content: "→";}
at the output in css it turns into a krakozyabra.
I tried to install charset both in the main less file and in the one in which these characters are, it does not help.
For half a day I thought that these were encoding problems on the server and / or files, but it turned out that at the time of compilation.

Answer 1

span:after {
    content: '\0439';
}
span:after {
    content: '\2192';
}

https://www.compart.com/en/unicode/U+2192