I recently had a project where I needed to turn a Russian text into an audiobook.
Most TTS/voice cloning services I tried were clearly focused on English voices, and the results in Russian were not great.
Eventually I found a voice cloning service that supports stress marks in Russian words (which is essential, since замок = castle and замок = lock are two very different things). That small detail made the audiobook sound much more natural.
For anyone curious, I even put together a comparison page with samples:
https://apihost.ru/voice-clone-comparison/
Might be useful if someone here is experimenting with non-English audiobooks.