~2007, Compiz wobbly windows and the desktop cube was my gateway via Ubuntu, after a few years shifted over to Debian with XFCE

This is definitely it, you beat me to it! Thank you

Is it LVM2? If you need a GUI I recommend: Blivet-GUI from a bootable USB environment so as you said nothing is mounted, hope this helps!

I have the exact same workflow except I have two images: one for legacy/MBR and another for EFI/GPT – once I read your post I was glad to see I’m not alone haha!

Started: ~2008 because I saw compiz had the virtual desktop cube & wobbly windows animations. Now I’m on Debian.

I’m a bit late here but when installing grub to a USB drive with a GPT/EFI compatible partitioning, you need to run the following command: “grub-install --target=x86_64-efi --efi-directory=/boot/efi --removable” (without the quotes).