Try it in a virtual machine

The virtual machine

Any UEFI virtual machine will do, for instance GNOME Boxes or virt-manager. BIOS is not supported: the ISO boots in UEFI mode.

• 8 GiB of memory: the live session runs in memory, its temporary files included.
• A blank virtual disk, used only by the installation.

These values are margins, not measured minimums.

With QEMU

From the folder that holds the ISO, with the OVMF paths of Fedora:

qemu-img create -f qcow2 indiga-installe.qcow2 64G
cp /usr/share/edk2/ovmf/OVMF_VARS.fd OVMF_VARS_indiga-installe.fd
qemu-system-x86_64 -accel kvm -cpu host -m 8192 -smp 4 \
    -drive if=pflash,format=raw,readonly=on,file=/usr/share/edk2/ovmf/OVMF_CODE.fd \
    -drive if=pflash,format=raw,file=OVMF_VARS_indiga-installe.fd \
    -drive file=indiga-installe.qcow2,if=virtio,format=qcow2 \
    -cdrom indiga-x86_64.iso

On Debian and Ubuntu, the paths are /usr/share/OVMF/OVMF_CODE_4M.fd and /usr/share/OVMF/OVMF_VARS_4M.fd. The disk is sparse: it only takes the space written to it, and 64G is a margin as well.

After the installation, run the same command without -cdrom: the UEFI variables file keeps the boot entry.

The live session

1. At boot, the menu offers two entries: Try or install indiga, and its variant in basic graphics mode, Try or install indiga (basic graphics mode).
2. The session opens without an account.
3. Firefox and the applications shipped in the ISO open without a network.

Nothing is written to the disk, and nothing survives a restart: what you do in the live session is lost when it shuts down.