After upgrading to 2023-09-18, I had a problem with Openfortigui, or any software using PPP to connect to Fortinet VPNSSL (probably others VPN but I can not say). The error message is “Peer refused to agree to his IP address”.
So the solution is to rollback ppp and networkmanager-pptp :
downgrade 'ppp=2.4.9-3' 'networkmanager-pptp=1.2.12-1'
… or