It has been some time since Ive booted another distro on Qubes and I recall being able to attach my TailsOS usb drive in Qubes and boot from in a vm.
Whenever attach the whole volume block it states no boot and likewise attempting with selecting different partition blocks within it does the same(as expected). Ive tried with Kicksecure as well with no success.
I recall this being possible, and from the different documentation I read again about standalone HVMs and usb/block data supports this. Images within a qube works, but wish to boot from my usb devices within qubes.
instead of using qvm-start Tails --cdrom=isoVM:/home/user/Downloads/tails.iso
you can go to your HVM’s settings → advanced en select “Boot qube from DISC or block device”
maybe I misunderstood but it seems that you said you were trying with your TAILS key. However, you can’t boot from your TAILS key but only from the.iso file As @barto said, just download the.iso image and boot directly on it with your HVM