I like Magic Earth on Android. I admit to not having done thorough investigation on all the privacy aspects, but the FOSS solutions cannot (could not?) offer me voiced directions in my own language without installing the Google voice pack software and I only use navigation about three times a year, so I stuck with Magic Earth.
Other TTS engines can surely work, yes, but I have found none that support my language and I prefer getting directions not in English :-). Magic Earth comes with TTS for my language and also worked on my previous Android phone, which was close to stock Android (LineageOS without Google Play).