Based on ssh-audit scanning and tested on VyOS 1.4.4:

Ciphers:

set service ssh ciphers chacha20-poly1305@openssh.com
set service ssh ciphers aes256-gcm@openssh.com
set service ssh ciphers aes128-gcm@openssh.com
set service ssh ciphers aes256-ctr
set service ssh ciphers aes192-ctr
set service ssh ciphers aes128-ctr

MAC:

set service ssh mac hmac-sha2-256-etm@openssh.com
set service ssh mac hmac-sha2-512-etm@openssh.com
set service ssh mac umac-128-etm@openssh.com

Key Exchange:

set service ssh key-exchange curve25519-sha256
set service ssh key-exchange curve25519-sha256@libssh.org
set service ssh key-exchange diffie-hellman-group16-sha512
set service ssh key-exchange diffie-hellman-group18-sha512
set service ssh key-exchange diffie-hellman-group-exchange-sha256

Host keys:

set service ssh hostkey-algorithm ssh-ed25519
set service ssh hostkey-algorithm ssh-ed25519-cert-v01@openssh.com
set service ssh hostkey-algorithm sk-ssh-ed25519@openssh.com
set service ssh hostkey-algorithm sk-ssh-ed25519-cert-v01@openssh.com