You can disable IPv6 at the level of a network interface or globally at the operating system level. In Windows Server 2019 follow the steps below:
- Run regedit.
- Navigate to registry key HKEY_LOCAL_MACHINE, SYSTEM, CurrentControlSet, services, TCPIP6 and Parameters.
- Right click on Parameters and select New and then DWORD (32-bit) Value. Name the new value DisabledComponents and hit Enter. Double click the new DisabledComponents value and select Modify.
- Set the value of DisabledComponents to FF and click OK.
- After a reboot IPv6 will be disabled on all interfaces.
Also review Microsoft article KB929852 which states that DisabledComponents should be set to FF instead of the previously communicated FFFFFFFF.