Antwort ist JAIN!
TTS is working only for TTS voices with VocalizerEx2 or some other external engine. You just copy TTS voice file in .../content/voice.

tts_nua_ve1 TTS is not working (for me), because it needs license. You can buy it, if you need it, it's only 5€. I didn't bought it, 'cause I don't need it, no Serbian available.
Serbian Lana is on VocalizerEx2.

Try it, my friend... Make a same structure as in iGO_xxx data folder, and try what works.

Spoiler: screen
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My phone is rooted, so I have made in sys.txt secondary root path to my iGO content folder on SD Card, so I can easily see what works and what not works.
Secondary root path can be defined also for non-rooted phones, @bb2005 made a branding.zip for it.