With a click on Next to proceed with the GroupShare installation, the following error is displayed:

Connection Timeout Expired. The timeout period elapsed while attempting to consume the pre-login handshake acknowledgment. This could be because the pre-login handshake failed or the server was unable to respond back in time. The duration spent while attempting to connect to this server was [Pre-Login] initialization=26296; handshake=26229;

Add an inbound rule to the firewall with the relevant ports on the Windows Server where the Microsoft SQL server is installed.

Defaults ports used by MS SQL are:
TCP 1433
UDP 1434

Open the relevant ports by adding an inbound rule to the firewall with the relevant posts. Defaults ports used by SQL is TCP 1433 and UDP 1434.
If a hardware firewall is used, ensure that the ports are also opened there.

The port (default TCP 1433, UDP 1434) is blocked or not opened on the server where the Microsoft SQL server/instance which hosts the GroupShare databases is installed.