In V14 application using MPR, legacy components are not attached to view after adding the font-awesome-iron-iconset add-on dependency. Here is a very simple reproducible example. If you run the application in production mode, or build the frontend even in development mode, it works fine.
The issue is the <g id="vaadin"> in fab.js which overrides the window.vaadin scope in the browser where the Framework bootstrap /framework/VAADIN/vaadinBootstrap.js sets the initApplication function [window.vaadin = window.vaadin || { initApplication: function(appId, config) .... ]. This doesn't work as window.vaadin returns the <g id="vaadin"> item and the framework intialization is never done as the initApplication is never added to the page.
To fix this the font-awesome-iron-iconset should rename the VAADIN icon to VAADIN_ICON in FontAwesome.java and vaadin-icon in fab.js
In V14 application using MPR, legacy components are not attached to view after adding the font-awesome-iron-iconset add-on dependency. Here is a very simple reproducible example. If you run the application in production mode, or build the frontend even in development mode, it works fine.
In https://github.com/vaadin/multiplatform-runtime/issues/120 it was commented that