I am stunned, given the robust way that the majority of MS tools which accept both command line and configuration file-driven arguments handle things, i.e. the command line overrides the configuration file, that the installer for SQL Server can be so spectacularly awful!

If you specify the '/Q' argument on the command line and your configuration file also contains an entry for 'UIMode', you will get this error:

Media ScenarioEngine.exe returned exit code: 0x858C001C

Crystal clear, right? Obscure text, meaningless error numbers...SMH...

Luckily, the log written to the bootstrap location (e.g. "C:\Program Files\Microsoft SQL Server\140\Setup Bootstrap\Log\Summary.txt") tells you what's happened:

The /UIMode setting cannot be used in conjunction with /Q or /QS

Also luckily, I always use the extracted MSIs to install this junk so am able to work around this nonsense but I just thought I might save some other poor soul the heartache and wasted hours trying to decipher what the Hell prevents it working.