This is amazing! If you are looking for US EN and use a phone with arm64 I can recommend sherpa-onnx-1.10.27-arm64-v8a-en-tts-vits-piper-en_US-kristin-medium and sherpa-onnx-1.10.27-arm64-v8a-en-tts-vits-piper-en_US-norman-medium.
Edit: I don't seem to be able to get the engine to show up as a tts engine but it works well within the tts app itself. Hopefully I'll find a fix I've been searching for a good tts engine for android eBook apps.
That would then require running code from memory, which needs to be enabled in recent GrapheneOS. But all fine, they should absolutely do that as they obviously do that currently but during compilation.
Client app + wizard to select language and model type + downloaded model