I made this thing.
https://github.com/BladeScraper-Desi...rSky/tree/main
Requires an active Microsoft Azure subscription and a Speech resource group.
If you're already a user of Azure and/or know your way around a computer, using this should be fairly straightforward.
If you don't even know what Azure is, it might be a little less straightforward, but using the Readme combined with Microsoft's own documentation (links to which are included in the Readme where relevant), you may be able to get started with it.
Support for all Azure-compatible languages and voices (except for Azure's Multilingual voice support, which is not available at this time except in their native language).
Output folder structure and files are directly compatible with FrSky Ethos 1.5 (and indirectly compatible with Ethos 1.4.x and other radio systems).
See GitHub Readme.md for more info, notes, and usage.
EXTREMELY A WORK IN PROGRESS. Please use GitHub properly and report any issues. Suggestions and feedback always welcome. I have no idea what I'm doing.