v.21.1Backward Incompatible Changes
Removal of implicit substitutions file references from default config in ClickHouse update
inclreferences to substitutions file (/etc/metrika.xml) were removed from the default config (<remote_servers>,<zookeeper>,<macros>,<compression>,<networks>). If you were using substitutions file and were relying on those implicit references, you should put them back manually and explicitly by adding corresponding sections withincl="..."attributes before the update. See #18740 (alexey-milovidov).