Как легко конвертировать видео MKV в MP4

One easy way (requiring a terminal), is using FFMPEG.

First, open a terminal and install FFMPEG with this command:

sudo apt install ffmpeg

Now all you have to do to convert your video is this one single command:

ffmpeg -i <inputfile> <outputfile>

For example, in your case:

ffmpeg -i input.mkv output.mp4

FFMPEG will automatically detect/use the correct input and output formats.

Conversion may take a few minutes based on length and frame rate of video.