This is becoming ridiculous, a simple objective “using an external mic. to record video with the S21 has turned into a science project!” Come on Samsung!
I was attempting to use an external mic. for my S21 Ultra (using the USB port). Tied to use pro-Video and select USB as source for the mic., USB as source is greyed out. Then I downloaded and installed Samsung USB-C app. (because I was unable to record using an external mic.). No change, USB C as the source is still greyed out, can only record using S21 built in mic.
As a work around I decided that what I will do is record using another device for audio and mix the video from the S21. Mix using Adobe Premier Elements or MS Movie Maker. So, of course I will want to turn off the S21 internal mic. So I navigate to settings, Security and Privacy, select Privacy, and then select Microphone access and switch from On to Off.
All seems right until I attempt to record a video (normal or Pro mode). The S21 will not allow me to record video unless I turn on the built in mic.!!