I'd like to interject for a moment. There is also a tool called bat that is just cat with extra features. It prints out and works just like cat, but when the contents get too big, it works like less. The is syntax highlighting and works with git.
It's replaced my need for cat and less.
Ncdu looks pretty cool. I'll give it a spin! I've tried a good handful of TUI file managers but most of doesn't feel right, so I made my own little script in attempt to scratch that itch. Not completely satisfied with it but it works ¯(ツ)/¯