How to convert Javascript exported class to Kotlin/JS?

I am new to JS and to Kotlin/JS. I have the following minimal working Javascript code for a Plugin for Obsidian from an example. It works as expected:

var obsidian = require('obsidian');
class SomePlugin extends obsidian.Plugin {
    onload() {
        new obsidian.Notice('This is a notice!');
    }
}
module.exports = Plugin;

I was hoping to extend this plugin using Kotlin as I know the language, but I have some problems converting this to Kotlin/JS. My approach so far:

The runnable project can be found here on Github. Run gradle build to generate the build folder. It will fail in the browser step, but that step is not necessary. After the build the generated js file can be found in build\js\packages\main\kotlin\main.js.

main.kt

@JsExport
class SomePlugin: Plugin() {
    override fun onload() {
        Notice("This is a notice!")
    }
}
@JsModule("obsidian")
@JsNonModule // required by the umd moduletype
external open class Component {
    open fun onload()
}
@JsModule("obsidian")
@JsNonModule
external open class Plugin : Component {
}
@JsModule("obsidian")
@JsNonModule
external open class Notice(message: String, timeout: Number = definedExternally) {
    open fun hide()
}

Edit: Thanks to the comment of @S.Janssen I switched the module type to umd

build.gradle.kts

plugins {
    kotlin("js") version "1.5.20"
}
group = "de.example"
version = "1.0-SNAPSHOT"
repositories {
    mavenCentral()
}
dependencies {
    implementation(npm("obsidian", "0.12.5", false))
}
kotlin {
    js(IR) {
        binaries.executable()
        browser {
            webpackTask {
                output.libraryTarget = "umd"
            }
        }
    }
}

tasks.withType<KotlinJsCompile>().configureEach {
    kotlinOptions.moduleKind = "umd"
}

I don't actually need a result that can be run in the browser, but without the browser definition, it would not even generate a js file. With the browser part, an exception is thrown saying Can't resolve 'obsidian' in 'path\kotlin'. But at least a .js file is created under build/js/packages/test/kotlin/test.js. However the code is completely different from my expected code and also is not accepted by obsidian as a valid plugin code. I also tried some other gradle options. like "umd", "amd", "plain", legacy compiler instead of IR, nodejs instead of browser. But nothing creates a runnable js file. The error messages differ. With the legacy compiler it requires the kotlin.js file, that it cannot find even if I put it right next to it in the folder or copy the content into the script.

How do I get code functionally similar to the Javascript code posted above? I understand that it will have overhead, but the code currently generated does not even define or export my class by my understanding.

The error message that I get from obisidan debugger:

Plugin failure: obsidian-sample-plugin TypeError: Object prototype may only be an Object or null: undefined

The code generated:

    (function (root, factory) {
  if (typeof define === 'function' && define.amd)
    define(['exports', 'obsidian', 'obsidian', 'obsidian'], factory);
  else if (typeof exports === 'object')
    factory(module.exports, require('obsidian'), require('obsidian'), require('obsidian'));
  else {
    if (typeof Component === 'undefined') {
      throw new Error("Error loading module 'main'. Its dependency 'obsidian' was not found. Please, check whether 'obsidian' is loaded prior to 'main'.");
    }if (typeof Plugin === 'undefined') {
      throw new Error("Error loading module 'main'. Its dependency 'obsidian' was not found. Please, check whether 'obsidian' is loaded prior to 'main'.");
    }if (typeof Notice === 'undefined') {
      throw new Error("Error loading module 'main'. Its dependency 'obsidian' was not found. Please, check whether 'obsidian' is loaded prior to 'main'.");
    }root.main = factory(typeof main === 'undefined' ? {} : main, Component, Plugin, Notice);
  }
}(this, function (_, Component, Plugin, Notice) {
  'use strict';
  SomePlugin.prototype = Object.create(Plugin.prototype);
  SomePlugin.prototype.constructor = SomePlugin;
  function Unit() {
    Unit_instance = this;
  }
  Unit.$metadata$ = {
    simpleName: 'Unit',
    kind: 'object',
    interfaces: []
  };
  var Unit_instance;
  function Unit_getInstance() {
    if (Unit_instance == null)
      new Unit();
    return Unit_instance;
  }
  function SomePlugin() {
    Plugin.call(this);
  }
  SomePlugin.prototype.onload_sv8swh_k$ = function () {
    new Notice('This is a notice!');
    Unit_getInstance();
  };
  SomePlugin.prototype.onload = function () {
    return this.onload_sv8swh_k$();
  };
  SomePlugin.$metadata$ = {
    simpleName: 'SomePlugin',
    kind: 'class',
    interfaces: []
  };
  _.SomePlugin = SomePlugin;
  return _;
}));

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