<Sort of solved> "Unable to find a medium containing a live file system"

[gold_finger]

EDIT:  Just read your post under Introductions section of forum and see that you're not a beginner to Linux.  Skip past everything I wrote yesterday (in black) and go directly to bottom of this post (in blue).



Are you planning on dual-booting with Mint, or replacing Mint with LL?


If planning to dual-boot, boot into Mint, open a terminal and post back here with output of following command to display your current partition structure:

Code:

sudo parted --list

LL can not boot nor be installed in UEFI mode, so you need to make sure the USB is being booted in Legacy/Bios mode (may be referred to as CSM in the UEFI Settings for boot mode).


Computer may have a special key assigned to bring up a per session Boot Menu (not the main UEFI Setting/Setup Menu).  If you can use that it should show two choices to boot the USB -- one UEFI, one non-UEFI -- pick non-UEFI option.


EG.
Dell computers -- <F2> = main UEFI Settings; <F12> per session Boot Menu


HP -- <Esc> shows options to use either <F9> or <F10> for Settings or Boot menus.


Possibly you could see a quick message on screen during POST telling you what key to hit for Boot Menu.  Otherwise, lookup user manual for the computer to find out.


If you are booting in Legacy mode and still have problem, try making USB with the dd command as per Help Manual here.




EDITED INSTRUCTIONS:


USB boot problem may be due to boot mode.  LL can only boot in and be installed in Legacy mode, so make sure you choose that mode for booting the USB.

Don't know what mode you installed Mint in before, but if it's in UEFI mode then drive is using GPT partitions.  No need to change that to install LL in Legacy mode.  Just do your usual partition setup, but make sure you add one extra partition -- a small (1-16MB), unformatted partition flagged as "bios_grub".  Doesn't really matter where you put that partition.  Direct boot loader installation to /dev/sda, not the "bios_grub" partition.

If you are booting in Legacy mode, but still experiencing problems, create USB with dd command instead and try again.