LO wrong convert-to pdf cyrillic symbols

Using LO on Linux without GUI. When using loffice --convert-to pdf
Outcome file has rectangle symbols instead cyrillic.
Linux locale is ru_RU.
I think its fonts problem.
How to check?

Apart from any possible solution I suggest to upgrade to a recent release, as 5.4 is years old, specifically 5.4.0 is the first of all 5.4.x releases. Maybe the problem was already fixed meanwhile, if it was a problem of LibreOffice at all.