Audacious - OLD, PLEASE USE GITHUB DISCUSSIONS/ISSUES

Under File -> Settings -> Playlist -> Compatibility, try setting "Auto character encoding detector" to Russian. If that doesn't help, set it back to None and try adding the character encoding of the playlist you are trying to open under "Fallback character encodings" instead.

It doesn't help.
In list ( playlist or File->Open ) i see correct russian filenames. But when i try to play it, error message.

Please start Audacious with "LC_ALL=C audacious" to get English error messages.

pi@raspberrypi ~ $ LC_ALL=C audacious

• (audacious:3172): WARNING **: Error retrieving accessibility bus address: org.freedesktop.DBus.Error.ServiceUnknown: The name org.a11y.Bus was not provided by any .service files
  Cannot convert to locale (ANSI_X3.4-1968): /home/pi/Music/mp3_ringtone/проверка.mp3

(audacious:3172): Pango-WARNING **: Invalid UTF-8 string passed to pango_layout_set_text()
Cannot convert to locale (ANSI_X3.4-1968): /home/pi/Music/mp3_ringtone/проверка.mp3
Cannot convert to locale (ANSI_X3.4-1968): /home/pi/Music/mp3_ringtone/проверка.mp3

• (audacious:3172): CRITICAL **: local_fopen: assertion 'path' failed

--------------------------------------------------------
! Run OTHER FILE !
---------------------------------------------------------

pi@raspberrypi ~ $ LC_ALL=C audacious

• (audacious:2977): WARNING **: Error retrieving accessibility bus address: org.freedesktop.DBus.Error.ServiceUnknown: The name org.a11y.Bus was not provided by any .service files
  Cannot convert to locale (ANSI_X3.4-1968): /home/pi/Music/mp3_ringtone/Лепс_Берега.mp3

• (audacious:2977): CRITICAL **: local_fopen: assertion 'path' failed
  Cannot convert to locale (ANSI_X3.4-1968): /home/pi/Music/mp3_ringtone/Лепс_Берега.mp3
  Cannot convert to locale (ANSI_X3.4-1968): /home/pi/Music/mp3_ringtone/Лепс_Берега.mp3

• (audacious:2977): CRITICAL **: local_fopen: assertion 'path' failed
  Cannot convert to locale (ANSI_X3.4-1968): /home/pi/Music/mp3_ringtone/Лепс_Берега.mp3

• (audacious:2977): CRITICAL **: local_fopen: assertion 'path' failed
  Cannot convert to locale (ANSI_X3.4-1968): /home/pi/Music/mp3_ringtone/Лепс_Берега.mp3
  Gtk-Message: GtkDialog mapped without a transient parent. This is discouraged.

The problem is almost certainly the use of a legacy (non-UTF-8) character encoding without configuring Audacious correctly for it. Until we know what encoding it is, we cannot help you. You said "It doesn't help" but you didn't say what encodings you tried.

Also you should try a more recent version; there were some character encoding fixes in 3.6 and 3.7. It may "just work" once you upgrade.

Problem fixed!

Solution:
1. sudo dpkg-reconfigure locales
2. select all with starting "ru_RU"
3. set "ru_RU.UTF-8" as default
4. reboot
5. in Audacious: File -> Settings -> Playlist -> Compatibility, set "Auto character encoding detector" to Russian
6. Enjoy !

Thank you all !

Glad you could fix it. :) What was your default locale before?

I don't looked for default. Run dpkg-reconfigure for experiment... :)