Well if you happen to find a good app that does what you want on desktop, then you can complement it on Android with Markor , it’s “markdown native” and it has nice extra options like adding list elements, quick formatting etc. All based on markdown, can be easily switched between editor mode and preview(markdown rendered) mode.
I’m using one of the models here . It’s working for voice instructions for navigation in Organic Maps. It’s also showing in the text to speech menu in the android settings.
The app it’s based on (SherpaTTS) already exists on fdroid repos, but the APKs on that link has the model embedded already.