How to enable IRIS Text Analytics programmatically?

If you would like to do it with %Installer Manifiest, it is not going to be easy, unfortunately. CSPApplication there quite limited.

I can't just do it this way.

<CSPApplication Url="${CSPApp}" Directory="${CSPAppDir}" iKnowEnabled="yes"/>

You should first create simple csp application

<CSPApplication Url="${CSPApp}" Directory="${CSPAppDir}"/>

Add something like this method

ClassMethod EnableiKnow(pCSPName As %String = "") As %Status
{
  new $namespace
  znspace "%SYS"
  set props("iKnowEnabled")=1
  d ##class(Security.Applications).Modify(pCSPName,.props)
  quit $$$OK
}

But unfortunately, I also can't just call it from an installer, Invoke tag should be placed in Namespace tag. which is actually current namespace, but you should compute it first. This may help to declare a couple more default variables. Just place two first lines before your Installer generator

  do %code.WriteLine($c(9)_"set pVars(""CURRENTCLASS"")="""_%classname_"""")
  do %code.WriteLine($c(9)_"set pVars(""CURRENTNS"")=$namespace")
  quit ##class(%Installer.Manifest).%Generate(%compiledclass, %code, "setup")

And finally, you can add this to your installer. Place it after CSPApplication creation, but outside of Namespace tag.

<Namespace Name="${CURRENTNS}">
    <Invoke Class="${CURRENTCLASS}" Method="EnableiKnow" CheckStatus="true">
      <Arg Value="${CSPAPP}"/>
    </Invoke>
  </Namespace>