Qt OPC UA itself uses Qt Categorized Logging internally. We document the logging categories here. So where does all this chatter come from? The open62541 stack has its own logging mechanism which is used to provide some insight into the stack itself. A plugin API allows to customize where this output is sent to. The default implementation, which we used so far, writes everything to stdout.
The new approach
As we did not just want to mute the open62541 output, potentially losing important information, we wrote a small plugin for the open62541 logging API to redirect the low-level open62541 output into a set of additional logging categories, all under the common qt.opcua.plugins.open62541.sdk prefix. To e.g. completely silence the low-level logs you would set „qt.opcua.plugins.open62541.sdk.*=false“ as a filter.
Please have a look at the commit itself for the new categories. Updated documentation will be available with the Qt 6.1 release.