React + Electron: components from deps aren't laying out properly

I'm trying to use components from dependencies in a project mostly freshly forked from electron-react-boilerplate. The layout is messed up (see pic below). Tried react-chat-window, react-chat-widget, and react-datepicker, so it's across the board. Sorry if this is vague, but I don't know what else to say, and I'm hopefully missing something really basic. Anyone know?

I've also read the electron-react-boilerplate docs. My deps are in ./package.json as suggested, but I also tried putting them into ./app/package.json, which breaks it entirely. This SO answer about material-ui didn't help this either.

Here's the relevant part of my page component, pretty much the same as in the example for react-chat-window:

import React from 'react';
const electron = require("electron")
import {Launcher} from 'react-chat-window'

class TextRoom extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      messageList: []
    };
  }

  async _onMessageWasSent(message) {
    this.setState({
      messageList: [...this.state.messageList, message]
    })
    // send message to server...
  }

  render() {
    return (
      <div style={{}}>
        <Launcher
        agentProfile={{
          teamName: 'react-chat-window',
          imageUrl: 'https://a.slack-edge.com/66f9/img/avatars-teams/ava_0001-34.png'
        }}
        onMessageWasSent={this._onMessageWasSent.bind(this)}
        messageList={this.state.messageList}
        showEmoji
      />
      </div>
    );
  }
}

class RoomDialog extends React.Component {
  constructor(props) {
    super(props);
  }

  render() {
    return (
      <div>
      <TextRoom />
      </div>
    );
  }
}

export default function Room(): JSX.Element {
  return (
    <div style={{backgroundColor: "black"}}>
      <RoomDialog />
    </div>
  );
}

The result looks like a website missing its CSS or something:

Supposed to look like this:

This page on electron-react-boilerplate, which seems to only be findable via Google and not on their site, pointed me to edit app.global.css. Seems really wrong that I have to do this when the module already imports its own styles, but it worked:

Replaced the contents of app.global.css with:

@import "~react-chat-window/lib/styles/chat-window.css";
@import "~react-chat-window/lib/styles/launcher.css";
@import "~react-chat-window/lib/styles/emojiPicker.css";
@import "~react-chat-window/lib/styles/header.css";
@import "~react-chat-window/lib/styles/message.css";
@import "~react-chat-window/lib/styles/popup-window.css";
@import "~react-chat-window/lib/styles/user-input.css";