My organization is in the process of upgrading our ArcGIS server to 10.4.1 along with Arc Desktop, Catalog, etc. We use ArcGIS viewer for Flex for all internal applications. I read the list of deprecated features for Arc 10.3 and 10.4 and saw that the Flex Viewer was one of them. I understand that Flex hasn't received support or an update since 2014/15. My question is, if we upgrade our software to 10.4.1, will the Flex viewer simply not work anymore? These applications are crucial to daily tasks and I do not want them to stop working once we upgrade to 10.4.1. I am in the process of putting our GIS applications in the Javascript API but with all of the different applications we use, it will take a long time. Any help is greatly appreciated!