Forticlient 7.0 and 6.4 branch do not officially support ubuntu 22.04lts. For me the UI does not opens. Cli works fine. Officially checked with support on this.
I’ve installed forticlient 7.0.6 on my ubuntu 22.04 from their repo. Just used the ‘bionic’ tag in the ‘/etc/apt/sources.list.d/fortinet.list’. Works ok, but there is just a trial licence for the app, which is going to expire. I wish there is a working plugin for the network manager instead. The network-manager-fortisslvpn-gnome I tried allows me to connect to the vpn, but the traffick is flowing only between my computer and my company’s networks, with no access to the internet tho. You can also try openfortigui from the ubuntu’s repo.