Yes, that should be possible. I haven’t tried it though.
If you’re creating your own UE4 plugins that are not derivative of Epic’s, there is no reason you can’t release the source code in a public GitHub repository if you so choose. As long as you aren’t pasting Epic’s code in there, you own that plugin’s code and can do whatever you want with it. Each plugin can then have it’s own repository if that is most convenient for you.
–Mike