You are trying to log in to the Broadcom support portal and get the error "Unable to determine user identification method. Please contact your administrator for assistance"
ZScaler proxy settings causing the issue
Check whether your organization is using Zscaler as a proxy service. If yes, kindly check if the endpoint (https://login.broadcom.com/.well-known/webfinger) is whitelisted (or any other methodologies) on the Zscaler side to avoid issues.
Should you need any further assistance, contact Broadcom Customer Care