My description for SSH via SmartCard
Just tested it on my Librem5
On Client
vi .gnupg/gpg-agent.conf
enable-ssh-support
vi ~/.bashrc
export SSH_AUTH_SOCK=$(gpgconf --list-dirs agent-ssh-socket)
gpgconf --launch gpg-agent
reboot System
get SSH Key for Server authorized_keys
ssh-add -L
On Server paste SSH key
vi ~/.ssh/authorized_keys
Deactivate login on server via password (optional)
vi /etc/ssh/sshd_config
PasswordAuthentication no