"Applying transformation... DITAVAL file not found. Check if the DITAVAL file has been moved."
Of course it's not found: I've never asked for one. I occasionally use .ditaval files in my usual DITA environment, but I'm pointing FM19 at a small set of clean files where no conditions have been set up or applied. Even the interface understands that.
What do I do next/ what am I misunderstanding?
Are you using Structure -> Generate DITA-OT output?
No! I have a ditamap open, looking fairly like an FM book, so I've selected Publish – you know, a nice, easy, integrated approach :-} and an option available from the interface.
So thanks for the tip about Structure > DITA > Generate DITA-OT output. No error messages, which is something … just a new folder containing a log file that starts
BUILD FAILED C:\Program Files\Adobe\Adobe FrameMaker 2019\fminit\ditafm\DITA-OT\build.xml:49: The following error occurred while executing this line: C:\Program Files\Adobe\Adobe FrameMaker 2019\fminit\ditafm\DITA-OT\plugins\org.dita.base\build_init.xml:99: java.lang.UnsupportedClassVersionError: org/dita/dost/invoker/ExtensibleAntInvoker : Unsupported major.minor version 51.0