Testing out LE on spare drive

I'm not aware of LE is writing to NVRAM.

What I could image:

when you unplug both other drive (recommendeted !) during install of LE on an 3rd drive your drive order in the bios could change.

Take a photo before unplugging for adjustments afterwards.

unfortunately you said nothing about how you boot debian/win

debian's grub chainloads win ?

- I'm long time out of the windows world, but what I remember: Win is picky mixing drive order, so I would (don't know if really necessary) also remember the sata/nvme (?) ports where the drives are now plugged -

after LE install you could plug in both drives again and (maybe) adjust the boot order in the bios (your photo !).

both other OS'ses should work as usual, but your LE will probably nowhere show up in boot menues (as least during first boot).

I guess debian should pick up your LE as an bootable OS.

if not: you ever could start LE (and usually the other OS'ses) via Bios boot menue key (see manufactur manual, something like F8, F11, ...)

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if you're running with 3 drives:

and boot LE, LE will automount both (?) other drives to /var/media/ (unsure). No harm, LE operates in /storage. But don't blindly write data to /var/media/

if you boot win11 it will probably write a directory named "System Volume Information" to your LE drive in the directory /flash . No harm !

win11 will see from the LE drive /flash (fat filesystem, accessible, LE boot partition !) and /storage (ext filesystem, un-accessible and therefore offers to format it. Danger !!!)