That said, switching to something like GitHub doesn't necessarily mean developers all _have_ to use exactly the same workflow. For example, if you're more comfortable in the command line, there are tools like [hub][1] and [git-gitlab][2] available which let you perform common tasks in GitHub/GitLab using the CLI.
I just think that long-term it's better to have a good baseline user experience that devs can then extend with their own personal tools if they choose than to have a not-so-great one that _requires_ you to extend it with your own tools before it's anywhere near as good as what a well-designed Web UI provides out-of-the-box; even if in the short-term that means breaking some dev's workflows.
Obviously that doesn't mean you shouldn't try to maintain compatibility with developer's existing workflows wherever possible though. For example, GitLab and GitHub both let you reply to issues by email, and RocketChat has an IRC plugin that lets you connect RocketChat rooms to an IRC channel.