I can confirm that I'm also seeing these messages approximately every 5-10 seconds:
{"log.level":"info","@timestamp":"2024-06-08T17:37:43.990+0300","message":"'ca_trusted_fingerprint' set, looking for matching fingerprints","component":{"binary":"filebeat","dataset":"elastic_agent.filebeat","id":"filestream-monitoring","type":"filestream"},"log":{"source":"filestream-monitoring"},"service.name":"filebeat","ecs.version":"1.6.0","log.logger":"tls","log.origin":{"file.line":179,"file.name":"tlscommon/tls_config.go","function":"github.com/elastic/elastic-agent-libs/transport/tlscommon.trustRootCA"},"ecs.version":"1.6.0"}
{"log.level":"info","@timestamp":"2024-06-08T17:37:43.990+0300","message":"CA certificate matching 'ca_trusted_fingerprint' found, adding it to 'certificate_authorities'","component":{"binary":"filebeat","dataset":"elastic_agent.filebeat","id":"filestream-monitoring","type":"filestream"},"log":{"source":"filestream-monitoring"},"log.logger":"tls","log.origin":{"file.line":199,"file.name":"tlscommon/tls_config.go","function":"github.com/elastic/elastic-agent-libs/transport/tlscommon.trustRootCA"},"service.name":"filebeat","ecs.version":"1.6.0","ecs.version":"1.6.0"}
{"log.level":"info","@timestamp":"2024-06-08T14:37:47.624Z","message":"Running on policy with Fleet Server integration: fleet-server-policy","component":{"binary":"fleet-server","dataset":"elastic_agent.fleet_server","id":"fleet-server-default","type":"fleet-server"},"log":{"source":"fleet-server-default"},"ecs.version":"1.6.0","service.name":"fleet-server","service.type":"fleet-server","state":"HEALTHY","ecs.version":"1.6.0"}
I'm running Fleet-server enabled Elastic Agent 8.13.4 as a Docker container.