Doesn't seem to be able to handle ed25519 keys.

[lwatsondev]

Feb 08 01:50:52 firefly.revthefox.co.uk minecraft[582785]: [SSHD] Failed to process public key /var/lib/minecraft-server/server/plugins/SSHD/authorized_keys/lwatson Failed (IllegalArgumentException) to parse key entry=ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIFWLwGNmandr8fQGj12xQAfHP/q05h8RJwPZ+RfCuOB8 rev@revthefox.co.uk: Bad format (no key data delimiter): rev@revthefox.co.uk

The file in question contains nothing but ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIFWLwGNmandr8fQGj12xQAfHP/q05h8RJwPZ+RfCuOB8 rev@revthefox.co.uk

[Justasic]

It seems to be a bug with the ssh library we use, I have filed an upstream bug as seen here: https://issues.apache.org/jira/browse/SSHD-974