QWC (QGIS Web Client) is a modular, responsive web client for QGIS Server, built with ReactJS and OpenLayers. With QWC you publish QGIS projects as web maps, with map display, search, printing, sharing, 2D and 3D editing, and multiple users or organisations each with their own views. The client runs as a static web application on top of QGIS Server; the separate qwc-services (Docker) add authentication, user management, roles and single sign-on, among other things.
QWC is developed within the QGIS organisation and licensed under the BSD licence; the source code is in the QGIS repository on GitHub. According to its statutes, QGIS.ORG is a Swiss association. You install QWC on your own servers, so map data and user management stay under your control. According to the project site, commercial support is available from companies such as Sourcepole, Oslandia and norBIT.