I frequently use OsmAnd as a navigation aid while driving, with turn-by-turn instructions spoken out loud using the default Pico TTS as the speech engine.

When driving with other people in the car, they are almost all irritated by how unnatural the default (French, female) voice sounds, especially compared to other TTS engines.

Is there any better, more natural sounding, offline, free/libre alternative to Pico TTS for Android (that supports French language)?

I'm most exclusively running LineageOS 13+ on my devices.

Please note that for versatility reasons, I'm not looking for pre-recorded voices, but synthesized ones.

Thank you for your input. :)