I didn't find any 'native' tips about this online; so I'm leaving it here.
Google Photos, a few months back, added the feature to remove/mute the audio on your video files shot on an Android phone. This is similar to what Photos app on iPhone does.
Open Photos (the default Google gallery browser, not your phone manufacturer version) on your Android phone
Open the video you want to remove the audio from
Press the edit icon which looks like three slider controls
Press the speaker icon and it will have a stroke appear on it
Press save a copy
Done