Set terminal window to the size of 104x14 characters (834x240px). Disable KDE effects and make sure Peek is installed and configured to start recording after 1 second by pressing CTRL+ALT+E and using 20 FPS.

Then get the window ID where the typing will happen:

WIN_ID=$(printf '%d' $(xwininfo | grep -Po '(?<=xwininfo: Window id: )(0x[a-f0-9]+)'))

Automatically start recording and typing and then stop recording:

xdotool \
  windowactivate $WIN_ID \
  key ctrl+alt+e \
  sleep 2 \
  type --file demo.input --delay 100 && \
xdotool \
  sleep 2 \
  key ctrl+alt+e

Optimize final GIF by using ezgif.com, compression level 35.