I tried to figure out how to do this, so that Git Cola would work properly and I could use multiple different GitHub accounts, but couldn't: https://git-cola.readthedocs.io/en/latest/git-cola.html#ssh-... which is a shame because I rather liked that program (staging individual chunks of code and lines within GUI software feels easier than doing the same for entire files with the CLI, in addition to having a visual look at the operations you're about to do)

In the end, I just gave up and forked over some cash for GitKraken, where it's as easy as clicking on a dropdown, in addition to also being cross platform and faster to work with than something like SourceTree. They even have a complete documentation page that describes how to do this exact thing, and it works the same across multiple platforms (Windows and Linux in my case): https://www.gitkraken.com/blog/managing-mulitple-github-acco...

Sometimes paying someone who has solved your exact problem pretty well is the path of least resistance, versus trying to figure out everything yourself. That's more or less why I'm also paying for the JetBrains IDEs, even if most of the software I use is free/open source. Nothing wrong with various scripts and utilities, though!