How to install full linux to a usb drive like unetbootin

I have recently looked into linux as my mac is currently at 10.12 and I need to run newer apps but currently cannot get a new computer. I have decided to move to linux but I don't want to touch the hard drive lest it be damaged. For that reason, an install to usb seems fine. However, I don't want to install from a traditional installer like ubuntu's (in live mode). I want to use a system set up like unetbootin, where I can see the disk name (sort of) and I know that my mac os part is safe. My computer supports booting from usb. As for the distro, anything based on the latest ubuntu (so I can r

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