This config is valid in 1.3.5:
user einar { authentication { public-keys "einar ISNIC ED25519 Key" { key AAAA type ssh-ed25519 } } full-name "Einar B. Halldórsson" }
The config migration when upgrading to 1.3.6 strips the quotes so it become this invalid config:
user einar { authentication { public-keys einar ISNIC ED25519 Key { key AAAA type ssh-ed25519 } } full-name "Einar B. Halldórsson" }
I assume the fix would be to replace spaces with underscores or dashes