Assuming you have a client PC that is connected to a OpenVPN host.
For SSH through the VPN tunnel: https://askubuntu.com/questions/1069846/connected-to-openvpn-server-but-cant-ssh
On the Openvpn host:
$ sudo ufw enable
$ sudo ufw allow 1194/udp comment "Allowing OpenVPN Connections"
$ sudo ufw allow from 10.8.0.1/24 to any port 22 proto tcp comment "SSH allowed for VPN clients"
On the client side:
Make sure OpenSSH is installed and running and port 22 is open on the firewall.
Then: $ ssh [email protected] (change “user” to your login name on the server/host).