A lot of people here (and there) think that multibooting is quite hard with macOS, which actually the case with some systems (stupid mobos) and quite tricky in legacy mode, but as far as you're using UEFI, it's very VERY easy.
To begin with, I will start with UEFI mode, which is the easiest setup to do. This guide will cover different situations, and I will try to implement linux too for people who are into that. I don't know if I will put a legacy dualboot (with GPT, and not MBR) until I do some extensive tests.
Neither I, nor anyone here, is responsible for what you're doing. Any material/moral loss is under the user's responsibility, save anything worth saving before proceeding, by following this guide, you accept these terms, you have been warned.