How to create a Magento 2 Modal popup that cannot be closed?

I couldn't get an override of the modal.closeModal() function to work via mixins and also I think doing it via a mixin makes it override through the whole website on all modals, which I do not want. I only need it on this one modal.

I ended up by simply removing any trigger that will call modal.closeModal(). There are some other modal options you can use to achieve that:

1. I hide the close button on opening the modal with the opened option/event which will be triggered right after the modal has been opened
2. I'm overriding the keyEventHandlers.escapeKey option

So this is my final code:

require(
    [ 'jquery', 'Magento_Ui/js/modal/modal' ],
    function($, modal) {
        modal({
            autoOpen: true,
            responsive: true,
            clickableOverlay: false,
            modalClass: 'modal-custom',
            title: 'Popup',
            buttons: [{
                text: $.mage.__('Take me back to the homepage'),
                class: 'action close-popup wide',
                click: function () {
                    window.location.href = '/';
                }
            }],
            opened: function($Event) {
                $('.modal-header button.action-close', $Event.srcElement).hide();
            },
            keyEventHandlers: {
                escapeKey: function () { return; }
            }
        }, $("#popup"));
    }
);

I reckon using mixins in that case would be relevant.

You can try the following:

First in your module, create the following view/base/requirejs-config.js :

var config = {
    'config':{
        'mixins': {
            'Magento_Ui/js/modal/modal': {
                'Vendor_Module/hook':true
            }
        }
    }
}; 

Then create view/base/web/hook.js :

define([], function(){
    'use strict';    
    return function(targetModule){
        targetModule.closeModal = function(){
            return false;
        }
        return targetModule;
    };
});

With this mixin, you replace the implementation of the closeModal method with your own method. In that case, returning false would avoid closing the modal.

Side note: I hate you for doing this. Unclosable popups should be banned from the web.