How to use magicyuv & utvideo codec with ffmpeg
The following Linux command searches all codecs than can Encode anything containing ut.

  ffmpeg -codecs | grep --regexp="^ .E" | grep --ignore-case ut


and its output is:

 DEVI.S utvideo              Ut Video


so you can use:

ffmpeg -i ~/Videos/WebCam/me.mp4 -c:v utvideo -r 30 -c:a libmp3lame -b:a 512K /tmp/test.mkv


However:

ffmpeg -codecs | grep --regexp="^ .E" | grep --ignore-case magic


has no output at all on my version of ffmpeg, but if your version supports it, you will see an output and then you just use whatever is in the second column as per the example above for utvideo.