one can simply install NRR to a USB thumbdrive or SD card, it works.
responsiveness suffers a bit though, even on fast SD cards.
makes sense to fully encrypt the flash drive of course during install, it is a Calamares option.
then use the USB-3 stick on multiple computers, often without problems. ATI & nvidia may be a problem though on vintage hardware or others. for backup / restore use gnome-disk-utility / gnome-disks as usual