The standard speech abstraction layer for linux is called speech dispatcher. It acts as a bridge to many different synthesizers available on linux. I know there are packages for dotnet that can use speech dispatcher, let me look it up and dget back to you. I know the developer of stardew access, a mod for stardew valley which uses dotnet either wrote or uses a speech plugin that supports mac windows and linux. No idea about android though. Again I’ll look it up and get back to you.