PPTX is Microsoft PowerPoint OOXML document format. This command line showing how to convert multiple PPTX files to ODP. This can be considered as Microsoft PowerPoint to LibreOffice Impress document conversion. We use several PPTX files from several resources, we mention them below.
soffice --headless --convert-to odp *.pptx
Important note: close all LibreOffice windows before running this command, otherwise it won't work.
A sample result shown below from Jachimo template (left = PPTX, right = ODS):
We use some PPTX templates from resources below: