You need to ue your username as a prefix for your repository if you want to push it to Docker Hub. In the first case Docker interpreted skander.msalmi as a name of a registry. In the second case no prefix was defined, meaning that the registry should be Docker Hub and the owner is Docker Hub itself. This is how official images can be downloaded and your is not official of course.
This would have been worked probably:
sudo docker push skanderdocker10/alpine:latest
Of course, you need to add that tag to the image.
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