We are planning to deploy Azure Update Management for our on premises Linux environment with gateway, need to understand whether the gateway will communicate to redhat / cent os for download patches / azure will download patches and push to end clients.
AFAIK, the Log Analytics gateway does not interfere with the actual process of package download. It only proxies communication with the Log Analytics workspace and Azure Automation. Having said that, package downloads will be done via the same route that would be used if no gateway was in the middle. More details here.