Yes – I want to use two cards in the same card reader. An SD card as the source and a micro SD card as the destination. I tested it out, and it seems to work OK as long as I put the destination card into the card reader first, then wait a few seconds, then put the source card into the same card reader.
Regarding using the internal system card as the backup destination: I have not been able to get that to work. The light on the card reader blinks, then the Raspberry Pi shuts down, then I put the system micro SD card into a card reader to view the contents on my Mac… and there is no folder of image files (just the regular Raspbian Lite system files).
While I’m at it… The card I’m using for my Raspbian system is a 16 Gig card. I formatted it on a Mac with the “SD Card Formatter” app, then I flashed the Raspbian Lite image to it using BalenaEtcher. When I mount the card on a Mac and look at it in Disk Utility, it shows up as having two volumes – a 268.4 MB volume (with 208.8 MB free), and an unnamed 15.66 GB volume that I can’t access at all on my Mac.
What happened to all my space???
p.s. I am fairly competent with a Mac, but I know almost nothing about Linux.