Seems like the args should be:
/VERYSILENT /SUPPRESSMSGBOXES /NORESTART /SP-
In Updates for Windows Applications Extended, we are using:
wait __Download\WinSCP-Setup.exe /verysilent /allusers /norestart /nocloseapplications /MERGETASKS=!desktopicon
If you look at the analysis of the setup file on VirusTotal, you will see “This installation was built with Inno Setup.”
You will also see results for “TrID” and “DetectItEasy” on VirusTotal that both point to this being likely an Inno Setup based installer.
So then you would look for the silent install switches for Inno Setup based installers: https://jrsoftware.org/ishelp/index.php?topic=setupcmdline
There are generally about 6 different types of EXE installers. Once you figure out which type you are dealing with, that dictates what the typical silent install commands SHOULD be, but then there can be some application specific additions that might be required depending on what you want as the outcome.