During these days I was wondering if it is possible to disable the Cisco ASA VPN page and continue to use SSL vpn with the client. These question was rasing due to security concerns about, a.e., AD user locking out.
Using ASDM you need to follow below steps.
Configuration > Connection Profiles > Check the box "Shut down portal login page"
This features seems to be confirmed in this very exhaustive article too:
https://www.linkedin.com/pulse/shutting-down-webvpn-portal-ftd-flexconfig-matt-albrecht
[original articles]
https://community.spiceworks.com/topic/2114883-disable-anyconnect-ssl-vpn-portal-website
https://community.cisco.com/t5/vpn/disabling-clientless-browser-based-vpn/td-p/3065988