You need USB Boot? Just load the ISO file into a virtual CD/DVD Drive and boot it.
No it does not need a gnome-session. It can run in KDE, XFCE and whatever Desktop Environment.
It just depends on some packages from gnome.
$ pactree -c -d1 gnome-boxes
gnome-boxes
├─cdrtools
├─edk2-ovmf
├─gtksourceview4
├─gtk-vnc
├─libarchive
├─libgudev
├─libhandy
├─libosinfo
├─libsecret
├─libvirt-glib
├─mtools
├─qemu-desktop
├─spice-gtk
├─tracker3
└─webkit2gtk
Yeah, maybe better ask for support there. Since they offer that application and you bought the expensive camera.