My primary handle is "KAction", which dates back to age when I believed that KDE -- huge, bloated and buggy mess of C++ code -- is cool. Now it is just a handle I am used to. I also sometimes use "iu" handle, but it is too short for the majority of web sites.
The main reason I have account on Github is to make pull requests to projects that have elaborate workflow, tied to Github, like Stackage or Nixpkgs. I hate it, but sometimes I really need patch applied upstream.
In theory, Gitlab is better then Github -- it is mostly Free Software. In practice, there is little difference -- same awkward interface, tailored to button smashing, with scripting and console interfaces supported as afterthought, if at all. Still, after Debian Alioth was decomissioned, I needed new home to my project, so for some time I used GitLab, until...
I found SourceHut. It's API is nice and simple, it includes CI system and, killer feature -- mailing lists service. Unfortunatey, most of projects I care about still use GitHub.