Galaxy Book Flex does NOT boot off non-UEFI USB sticks. (no Legacy mode e.g.)

I am upgrading my TiVO drive from 3TB to 8TB. This requires a few steps (including for example removing the HDD from the TiVO which is easy). Anyway, the key step is booting the computer, which the TiVO old HDD and new HDD are attached to, off a Linux-based image of software called MFS Tools. This is needed to run some commands to copy my current 3TB * TiVO drive over to the new larger drive (8TB in my case) and another command twice to increase the partition size (add 2TB at a time to get to 8GB - 1st copy command makes it a 4TB partition).

Anyway, I found out the hard way, that the Galaxy Flex (like many newer laptops it seems per a relative) does NOT support booting off a NON-UEFI drive (no 'Legacy' mode or equivalent in the Flex's BIOS).
I also own an Acer Predator laptop. This one supports booting off the non-UEFI USB flash drive with the Linux tools, but it had some odd error while booting the Linux image / tools (did not have time to troubleshoot why).

So I had to resort to using an an older 18.4" 8943G Acer laptop (still i7 but panel image was dull compared to current laptops and it had also become sluggish in recent years) which only has USB 2.0 ports.
Copying 3 TB at USB 2.0 speeds ~ 50 hours with that software!

Anyway, just posting this to save others headaches with similar non_UEFI images / tools wasting their time troubleshooting thinking there is something wrong with their disk image causing it not to boot, when it is simply the Flex not supporting NON-UEFI boot ('Legacy' boot option on the Predator).

* I am starting wih a 3TB TiVO drive since I had already done a simple swap from 500GB OEM drive to a larger 3TB drive as soon as I got the TiVO - this was as easy as swapping the drive out and letting the TiVO format and prep it fully automatically since it was within the supported size limit and I had no recordings yet at the time)

 

Did you have any luck with a live USB boot? I don't think that requires legacy boot support (or at least it didn't on my 3-yr old HP Spectre). I found this thread on reddit, and it looks like one can at least get Linux to boot on the Flex (though maybe not everything works out of the box).

https://www.reddit.com/r/Fedora/comments/f22pvf/samsung_galaxy_book_flex_fedora_live_usb_stuck/