edit /lib/systemd/system/greenbone-security-assistant.service

ExecStart=/usr/sbin/gsad --foreground --listen=0.0.0.0 --port=9392 --mlisten=0.0.0.0 --mport=9390  --allow-header-host my-public-IP  --timeout 1440


systemctl daemon-reload && systemctl restart greenbone-security-assistant.service
openvas-stop
openvas-start

https://my-public-IP:9392