Cannot insert mp4 in Writer

Tried to insert an MP4 video in a writer document I was working on. To no avail. The only thing Writer did, is transforming the file into a picture. Clicking on that picture did not open the video.

Is there something I have overlooked, or is this something LibreOffice as yet is unable to process?

Grateful for any help.

Try starting LO from the command line e.g., using soffice or similar. This should then report any issue to the terminal that LO may be having with the MP4. For example, with one MP4 here I receive this message:
** Message: don't know how to handle video/x-h264, stream-format=(string)byte-stream, alignment=(string)au, level=(string)3, profile=(string)high, width=(int)640, height=(int)360, framerate=(fraction)25/1, pixel-aspect-ratio=(fraction)1/1, parsed=(boolean)true