Linux

Very, I only really use my mouse for playing video games at this point. You don't really NEED to use Emacs/Vim/etc, but they do help a lot. Ranger (file manager), cmus (music player), qutebrowser (web browser, full featured unlike Lynx, which I do still like, but I use eww in place of it most of the time), etc, etc. Tons of stuff that can make your setup far, far less mouse dependent. Starting with learning the terminal, then using a twm is how I got to the point where I am now where all non-necessary mouse functions are replaced by keyboard keys. Just note that it did take about ten years to get here, though that wasn't me actively searching for ways to do it, more just naturally making my computer work how I wanted it to without the specific end-goal of zero mouse usage.

Edit: Forgot to include that I did most of this before learning Emacs at all. I've used nano for most of my time on Linux, only switching to Emacs last August. Only thing I didn't have before that was cmus. It also works as an email client, but ehh... I don't feel a strong need to switch away from Thunderbird at this point in time.