Remove audio from mp4 file is asking a specific question and demonstrates that user tried to find a solution.
It was closed as duplicate of What's video converters are available for Ubuntu? despite that conversion between sane video formats will not remove sound and that this question is closed as too broad.
I am posting here as recommeded by How can I request for a question to be reopened which was incorrectly closed as a duplicate?
For now, you can try posting in the meta site