Problem with 1.9.23 KMP version. It's been fixed in 2.0 so it needs to be updated

sample/src/wasmJsMain/kotlin/com/ionspin/kotlin/crypto/sample/Main.kt

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+
+
+import com.ionspin.kotlin.crypto.LibsodiumInitializer
+
+
+fun main() {
+     LibsodiumInitializer.initializeWithCallback {
+//        val hash = Hash.sha512("123".encodeToUByteArray())
+//        println("Hash (SHA512) of 123: ${hash.toHexString()}")
+         println("Hello")
+     }
+}

sample/src/wasmJsMain/resources/index.html

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+<!doctype html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <title>Libsodium bindings sample app!</title>
+    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css" integrity="sha384-Vkoo8x4CGsO3+Hhxv8T/Q5PaXtkKtu6ug5TOeNV6gBiFeWPGFN9MuhOf23Q9Ifjh" crossorigin="anonymous">
+</head>
+<body>
+<div id="root"></div>
+<script src="sample.js"></script>
+</body>
+</html>