If I try and print mailmerge either to a file or to the printer neither works.
Saving to a file - A filename is requested, but no file is created.
Printing a standard document - Works fine
Printing a mailmerge = No printer dialogue box appears to select number of copies or other details and nothing gets printed.
“Use OpenGL” and “ForceOpenGL” are both unchecked (which was the solution to the similar Q61106).
Libre Office 184.108.40.206 (just uploaded the latest version) on Ubuntu 16.04 LTS.