On proxmox I was getting this error when connecting through SSH
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = (unset),
LC_ALL = (unset),
LANG = "en_US.UTF-8"
are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
Has to do with some locale that can't be loaded.
Fix:
Remove/Comment this line in /etc/ssh/sshd_config:
AcceptEnv LANG LC_*
Restart SSHD