Fortivpn does offer 2 clients for linux, one is for redhat family and the other installer is for ubuntu/debian family. You can download the installers from here.
But for those who wanted to used opensource vpn client to connect to Fortinet VPN, we can use openfortivpn. Please follow below steps to connect using openfortivpn
1. Install openfortivpn
$ sudo apt install openfortivpn
2. We can connect just by using openfortivpn with some options, like below
$ sudo openfortivpn myvpnserver.local:10443 -u vpnuser -p mypass
where:
-u : please provide username
-p : please provide password
myvpnserver.local:10443 : please provide vpn server address and port
3. We can also use a configuration file with content like below
host = myvpnserver.local
port = 10443
username = vpnuser
password = mypass
save the above file as myvpn.config and connect using below command so that openfortivpn can use the configuration inside the file to connect to vpn
$ sudo openfortivpn -c myvpn.config
4. We can get all the configuration for the file, by referring to the manual page of openfortivpn. We can access the manual by running below command
$ man openfortivpn