We stream our community demos on youtube via Google Meet and there are borders on each side which makes the content to be smaller and less readable. Luckily, it is in the middle of the screen, so the following command will crop the image to its 1/1.29 of the size, stretch it back to 720p and reencodes it for YouTube copying the audio stream.

ffmpeg -i intput.mp4 -vf "crop=iw/1.29:ih/1.29,scale=-1:720" -y output.mp4

If your source video is different, just play around with the 1.29 constant to get the desired output. Use -t option to encode just the first 10 seconds of the video to speed testing up:

ffmpeg -i intput.mp4 -vf "crop=iw/1.29:ih/1.29,scale=-1:720" -t 00:00:10.0 -y output.mp4

That is all.