Godot 4 has a workable text-to-speech API under DisplayServer. This works on Linux, provided you install the requisite third-party libs. In my case, on Manjaro, this included installing spd-say, festival, and espeakup.
When I got text-to-speech working, I then exported my project for Linux. Running the executable works fine (the text-to-speech works). When I gave it to someone else who didn't have the right libraries installed, they got an error (no voices available).
Is it possible to create a self-contained export for Linux that includes everything needed for text-to-speech to work?