I have a 2015 MacBook Air and plan to triple boot MacOS, Arch Linux and Ubuntu by installing Arch and Ubuntu onto my SSD. I have looked at this thread and read about installing rEFInd onto the SSD so that the default macOS bootloader is left unchanged. I have also read through this article and plan to do something similar.
From the article I have read that you must install Windows first before installing Ubuntu. I completely understand how to install Ubuntu after installing Windows.
The part that I am confused about is how to do this but install Arch Linux instead of Windows. If possible I would like full list of steps of how to install Arch Linux on the SSD.
Thanks in advance!
TL;DR: Trying to triple boot Arch and Ubuntu from an external SSD using this article but I am unsure how to install Arch Linux first instead of Windows.
Note: I am fine using other methods of triple-booting Arch and Ubuntu as long as it doesn't make changes to my mac.
Model: 2015 MBA
macOS Version: Catalina (10.15.3)