Linux

Proper touch typing is a dramatic increase to ergonomics and efficiency, and will reduce strain overall. Your wrists shouldn't be moving much if at all while touch typing. There are lots of free online resources available for you to learn how to touch type quickly (and properly). When I first learned how to touch type after years of looking at my keyboard, I got from 0 to 30WPM in a few days of spending a couple hours each day. After a week, I had almost doubled my WPM before learning touch typing, at 60WPM. It's a very important skill that you will be glad you learned if you have regular interactions with computers.

But I understand that this is beyond the scope of your original post.

As far as portability is concerned, you will find vi (the predecessor to vim) on basically any Linux system you will ever run across. It works consistently and is installed by default basically everywhere. I used to hate vim, but after taking the minimal amount of effort to learn neovim, creating my own keybinds, and installing plugins, I've come to absolutely love it. It just takes a small amount of time to wrap your head around switching between insert mode and command mode (i to enter insert mode, escape to leave insert mode back into command mode, :w to save in command mode, and :q to quit in command mode (can combine to save and quit with :wq)), but after that it becomes quite intuitive.

You could even use a mouse with vim/neovim, though I would recommend keeping that usage to when you are scrolling through a large file quickly, looking for errors, etc. where you don't need to be actively typing. You can even turn it into an IDE with the use of language servers that will find compilation errors in files, similar to what you can achieve in something like VS Code. The possibilities are endless. Yes, it has a steep learning curve if you want to get incredibly efficient with it, but you can pick up basic editing in vim very quickly.