SOCKS Authentication in Qt Network and WebEngine

A working Qt Network proxy login does not establish that WebEngine supports the same SOCKS authentication. WebEngine uses Chromium, whose SOCKS5 implementation lacks authentication-method support; HTTP proxy login handling does not provide that exchange.

QNetworkProxy can store protocol, host, port, username and password. Two consumers reading those fields can still implement different protocols and methods.

For a Network-success/WebEngine-failure comparison, record the actual proxy protocol/method, Qt/Chromium versions and failed stage. Choose a route supported by the consumer making the request. For permitted public WebEngine browsing, the SOCKS5 proxy list offers candidates to check for unauthenticated access; use a separate configuration without carrying over another proxy's username or password. An unsupported method stops before website login, so changing the destination account addresses the wrong exchange.