(This is something that's cropped up for me mainly when using github, so I don't mind too much if any solution is github-specific. But the problem isn't github-specific per se, and any solution needn't necessarily be either.)
You can always clone a public github repo using https.
git clone https://github.com/my-user-name/SDL-mirror/
git clone firstname.lastname@example.org:my-user-name/SDL-mirror.git
What you can do is:
locally instruct Git to use ssh instead:
git config --global url.ssh://email@example.com/.insteadOf https://github.com/
That way, for your local repo, you are always using ssh, but for anyone cloning your repo, there are only https references.