what did your filebeat logfile in /var/log/graylog/collector-sidecar gives you back? What is the configuration in /etc/graylog/collector-sidecar/generated/filebeat.yml ?
what did your filebeat logfile in /var/log/graylog/collector-sidecar gives you back? What is the configuration in /etc/graylog/collector-sidecar/generated/filebeat.yml ?