Ugh. No. I still don't know how to just boot this backup. When I try it in an older laptop, the keyboard and trackpad stop working once I log in. I presume this is a hardware driver problem. Presumably that's unavoidable.

I am, of course, not eager to screw up the BIOS settings on my daily laptop.

I couldn't figure out how to boot the cloned drive in a VirtualBox VM. The tutorials seem to assume that I have a virtual disk image or enough internal hard disk space to copy the cloned drive locally in order to run it locally. That defeats the purpose.

So I'm stuck. If I can't just boot to the USB external drive because of UUID clashes, then I don't know what I'm supposed to have gained by cloning my laptop's internal hard disk. I have a backup that I can't safely boot to. 🤷

I continue to be grateful to anyone willing to try to help me understand how to do this. It's literally the only thing that stops me from feeling 100% comfortable with a Linux distribution as my everyday OS. I feel like I've been living with a ticking timebomb for the past eight years.

UPDATE: I booted to Pop!_OS, then used chroot, but this is not what I was expecting.