According to the documentation for the camel-sftp component it's possible to set a server_host_key with the value ed25519. However that algorithm is not available with Jsch.
As a result the documentation is confusing as it's proposing options that are not available.
When trying the parameter it will ignore ed25519 as jschProposal.
Please change at least the documentation to list: ssh-dss,ssh-rsa,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
Perhaps look into using the fork of jsch or other means to allow for ED25519 as algorithm.