In https://gerrit.wikimedia.org/r/c/mediawiki/core/+/1003568/1#message-7b4d72a20d278f68aba32d7a855647cfb726bdf4, SonarQube Bot complains about duplicated lines in machine-generated code (includes/config-schema.php).
Topic on Talk:Continuous integration/Codehealth Pipeline
I think the only way around that is using a sonar-project.properties file https://docs.sonarsource.com/sonarcloud/advanced-setup/ci-based-analysis/sonarscanner-cli/#use, to tell Sonar to ignore particular files.
Sonar recently made it possible to exclude source files through project settings in the portal. I have excluded the specific file from analysis; hopefully that is enough to solve the issue.