I think I have fixed the issue in the current unreleased version: I looked through the routing API definition and found how to request directions in more languages, including Russian.
some routing, no crashes so far + all the Cyrillic letters were displayed without problems, just the espeak Russian voice output could be better
The only problem was espeak reading Czech place names with english pronunciation, which is often quite funny But it worked even before without problems, most probably because our alphabet is basically just ASCII + čřžýáíéůú.