Use system espeak-ng instead of the bundled espeakng-loader package.
On Gentoo, espeak-ng is installed system-wide via app-accessibility/espeak-ng.

--- a/src/kokoro_onnx/tokenizer.py
+++ b/src/kokoro_onnx/tokenizer.py
@@ -4,7 +4,6 @@
 import platform
 import sys

-import espeakng_loader
 import phonemizer
 from phonemizer.backend.espeak.wrapper import EspeakWrapper

@@ -18,9 +17,9 @@
         if not espeak_config:
             espeak_config = EspeakConfig()
         if not espeak_config.data_path:
-            espeak_config.data_path = espeakng_loader.get_data_path()
+            espeak_config.data_path = "/usr/share/espeak-ng-data"
         if not espeak_config.lib_path:
-            espeak_config.lib_path = espeakng_loader.get_library_path()
+            espeak_config.lib_path = ctypes.util.find_library("espeak-ng")

         # Check if PHONEMIZER_ESPEAK_LIBRARY was set
         if os.getenv("PHONEMIZER_ESPEAK_LIBRARY"):