Salesforce LWC FullCalendar V5 Initialization Issue

Question

Having an issue with initializing V5.3.2 FullCalendar in Salesforce Lightning Web Component:

JS:

import { loadStyle, loadScript } from 'lightning/platformResourceLoader';

import fullCalendar from '@salesforce/resourceUrl/fullCalendar532';
// import fullCalendar from '@salesforce/resourceUrl/fullCalendar442';


export default class FullCalendarTestV5 extends LightningElement 
{
    async renderedCallback()
    {
        console.log(`## loading up calendar library...`);
        await Promise.all([
            loadScript(this, fullCalendar + '/lib/main.js'),
            loadStyle(this, fullCalendar + '/lib/main.css')

            // loadScript(this, fullCalendar + '/packages/core/main.js'),
            // loadStyle(this, fullCalendar + '/packages/core/main.css')
        ]).catch(error => {
            console.error(`## error: ${error}`);
        });

        console.log(`## loaded up calendar library...`);

        this.initialiseFullCalendarJs();

        

    }

    initialiseFullCalendarJs()
    {
        
        console.log(`## initializing calendar...`);

        const ele = this.template.querySelector("div.fullcalendarjs");

        console.log(`## ele: ${ele}`);

        let calendar = new FullCalendar.Calendar(ele, {});
        // calendar.render();
    }
}```

HMTL:

```<template>
    Full Calendar

    <lightning-card>
        <div id="calendar" class="fullcalendarjs slds-p-horizontal_small"></div>
    </lightning-card>
    
</template>

Error:

fullCalendarTestV5.js:4 Uncaught (in promise) ReferenceError: FullCalendar is not defined at s.initialiseFullCalendarJs (fullCalendarTestV5.js:4) at s.renderedCallback (fullCalendarTestV5.js:4)