Below is an end-to-end example you can try. Paste this HTML into your White Label - Custom Branding - Custom HTML, then log in as a customer account to try it out.

<script>
    function render({ container, close }) {
      const element = React.createElement(
        "div",
        { style: { display: "flex", justifyContent: "center" } },
        React.createElement(
          "button",
          {
            onClick: () => {
              window.location.href = "https://duda.co";
            // You can call close() function to close the popup
            },
            style: { display: "flex", justifySelf: "end" },
          },
          "Learn more!"
        )
      );
      ReactDOM.render(element, container);
    }
    
    window.addEventListener("load", function () {
      platform.events.on(
        platform.events.names.EDITOR_HOME_BUTTON_CLICKED,
        async (event) => {
          event.preventDefault();
                await platform.ui.openPopup("editor-home-button-popup", {
            width: 300,
            height: 400,
            render
          });
        }
      );
    
      platform.events.on(
        platform.events.names.AFTER_SITE_PUBLISH,
        async (event) => {
          event.preventDefault();
          await platform.ui.openPopup("after-site-publish-popup", {
            width: 300,
            height: 400,
            hideCloseButton: true,
            render
          });
        }
      );
    });
    </script>

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