I have no solutions sorry.
Dicio can do some commands and general speech input: “navigate to paris” will open the default Navigation and show Paris, but it will have issues recognizing country specific places or do anything beyond basic (“route from here to paris” will not work), you’ll need low expecations - dictation is pretty okay though. It has an “AA support issue” you can track. Did you try to install Google Assistant?
The AA docs will install the Google speech-synthesis package, so I think you do not take issue with the TTS quality. But if you do, SherpaTTS is the current goto for non robotic voice output and can be used from OrganicMaps.