(Where) are system configuration changes logged?

For what it’s worth @dan: SonarQube does let you track record all incoming HTTP requests if you wish to do so. Check-out sonar.web.accessLogs.pattern in sonar.properties. As Ann mentioned there is no functional changelog in the UI, but should you have any need to trace down a specific interaction with the SonarQube server, access.log can give you some visibility into that.