VyOS based on a lot of Debian packages but this is not Debian, On the boot message, we can see
Welcome to Debian GNU/Linux 10 (buster)! [ 15.187332] systemd[1]: Set hostname to <localhost.localdomain>. [ 15.194795] systemd[1]: Initializing machine ID from KVM UUID.
I propose to change this to Welcome to VyOS {version} {Release Train}
Need to modify /etc/os-release and add some hook to vyos-build