There is no terminal output of the prompt asking for confirmation to install an unsigned package. If the -V flag is specified, the message appears.
As a result, the installation seems to hang (it’s actually waiting for a “Y” input). When you press Enter, it terminates with an error.
In other words, without the -V flag, the following message is not shown on screen:
No valid signature found for saf-l1-1.1.8.
Do you want to proceed with the installation [y/n]?