So, you've got yourself a KaiOS device?

Is it a Nokia 8000 4G? If so, then this guide will most certainly help you.

Nokia 6300 4G? Yeah, I think they're similar enough.

other KaiOS 2.5.4 device? some of these tips might work for you

something else? - go here, most of the tips I'm giving are from there, I'll just try to explain them in a way so you don't have issues that I did following them

Step one - How to root your Nokia 8000 4G/Nokia 6300 4G in a way that doesn't cause too much trouble