Kibana behind firewall

Not sure about the other errors, but those seems to be related to the integrations as they are trying to connect to epr.elastic.co, which is the endpoint for the integrations packages.

Since a lot of things in Kibana now relies in integrations, I would expect some of them to not work right or throw some errors in the logs if it cannot access the epr endoint.

In this case you would need to have an air-gapped EPR as explained in this documentation.