Video editor for cutting a video into multiple short clips and store them quickly
shotcut
I would suggest shotcut. It's really fast and allows you to select where to cut at the right place (to the frame). It's also visual making it really easy.
Basic Setup

Start shotcut
Give your project a name
Drag &amp; Drop an MP4 in the screen video area
Click on the video now playing, move it to the timeline

Cut + Export

Click on the timeline time (top of the timeline) to select a location.
Click on the ][ icon to do a cut.
Right click on the left side and do &quot;Remove&quot;.
Click on the right side and do a &quot;Remove&quot; as well.
Then Export (File → Export Video ... | Ctrl-E).

Next Cut
Once the export is done:

Hit Ctrl-Z to restore the clip on the right side.
Then cut/remove again...
Repeat until done.


Under Ubuntu, I can install shotcut with:
snap install shotcut

ffmpeg
If you know the start point and duration, then you can use ffmpeg like so:
ffmpeg -ss 0:0 -t 5:0 -i in.mp4 out.mp4

The -ss defines the start point and -t defines the duration. You can use those two and create the cuts in the command line. You can always use shotcut or some other tool to determine the start/duration parameters.