Gespeaker is nice cross-platform and Open Source GTK+ front-end for the eSpeak speech synthesizer application (xcellent for linux)
https://linux.softpedia.com/get/Mult...er-48445.shtml
You can download through software manager on mint and the like os.
I have not been able to figure out a way to load into Reaper... but its a good stand alone... with like 100 languages male female formants etc.