Today I ran into the problem that a gitlab shell workload was reporting:
Error loading key "ssh_host_ed25519_key": invalid format
The private key looked similiar like this and great at first glance:
ssh_host_ed25519_key: |
-----BEGIN OPENSSH PRIVATE KEY-----
xxxxREDACTEDxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxx==
-----END OPENSSH PRIVATE KEY-----