I saw that to download the install file for Ubuntu is 6GB. Does this mean that I can install Ubuntu on any USB drive with a capacity greater than 6GB?
Thanks
The actual answer is "YES".
A very simple tool to use for writing the file onto the USB-drive is: Balena Etcher
The USB-drive will boot up as a pure Linux, if you select "Try Ubuntu" as it comes up.
There are tools for all normal tasks, as in creating media, accessing an installed Linux OS partition and so on... so consider the USB-drive to be your rescue if you need to do something special.
This system (24.04 scratch install, on a 4TB NVME) was setup from a USB-drive created with Balena Etcher,
Device Start End Sectors Size Type
/dev/nvme0n1p1 2048 2203647 2201600 1G EFI System
/dev/nvme0n1p2 2203648 6397951 4194304 2G Linux filesystem
/dev/nvme0n1p3 6397952 14786559 8388608 4G Linux swap
/dev/nvme0n1p4 14786560 7814033407 7799246848 3,6T Linux filesystem
... so not sure what the comment about legacy mode requirement (below) is about.