Installed https://launchpad.net/ubuntu/+source/livecd-rootfs/2.765.44/+build/28611104/+files/livecd-rootfs_2.765.44_arm64.deb in a jammy arm64 LXD container and ran commands from the Test plan:
ubuntu@jammy:~/build$ rm -rf auto local config
rm -f livecd.*.model-assertion
mkdir -p auto
for s in config build clean; do ln -s /usr/share/livecd-rootfs/live-build/auto/$s auto/; done
lb clean --purge
export PROJECT=ubuntu-core ARCH=arm64 SUBARCH=tegra-igx SUITE=jammy IMAGEFORMAT=ubuntu-image CHANNEL=edge
lb config
sudo -E lb build

[2024-06-28 13:46:32] lb_clean --purge
P: Executing auto/clean script.
[2024-06-28 13:46:32] lb_clean noauto --purge
P: Executing auto/clean script.
[2024-06-28 13:46:32] lb_clean noauto --all
P: Cleaning chroot
P: Executing auto/clean script.
[2024-06-28 13:46:32] lb_clean noauto --cache
[2024-06-28 13:46:32] lb_config 
P: Executing auto/config script.
Building on jammy.lxd
Configured ubuntu-image for the following model assertion:
type: model
authority-id: canonical
series: 16
brand-id: canonical
model: ubuntu-core-22-tegra-igx-edge
architecture: arm64
base: core22
grade: signed
snaps:
  -
    default-channel: 22-igx/edge
    id: 9pjCtYlNoT9Fx6RiHMhhBoIG6ZYXBvJc
    name: tegra
    type: gadget
  -
    default-channel: 22-igx/edge
    id: Rjyoy6Zhe9mlkBQqmVzaUdPB2TblFSwV
    name: tegra-kernel
    type: kernel
  -
    default-channel: latest/edge
    id: amcUKQILKXHHTlmSa7NMdnXSx02dNeeT
    name: core22
    type: base
  -
    default-channel: latest/edge
    id: PMrrV4ml8uWuEUDBT8dSGnKUYbevVhc4
    name: snapd
    type: snapd
timestamp: 2024-04-23T15:12:16+00:00
sign-key-sha3-384: 9tydnLa6MTJ-jaQTFUXEwHl1yRx7ZS4K5cyFDhYDcPzhS7uyEkDxdUjg9g08BtNn
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----------------------------------------------------------
[2024-06-28 13:46:32] lb_build 
P: Executing auto/build script.
WARNING: proceeding to download snaps ignoring validations, this default will change in the future. For now use --validation=enforce for validations to be taken into account, pass instead --validation=ignore to preserve current behavior going forward
Fetching snapd
Fetching tegra-kernel
Fetching core22
Fetching tegra

Worked fine, model assertion is correct and manifest is as expected:
ubuntu@jammy:~/build$ ls
auto
config
livecd.ubuntu-core-tegra-igx.img.xz
livecd.ubuntu-core-tegra-igx.manifest
livecd.ubuntu-core-tegra-igx.model-assertion
output
ubuntu@jammy:~/build$ cat livecd.ubuntu-core-tegra-igx.manifest 
core22 1522.snap
snapd 22283.snap
tegra-kernel 3.snap
tegra 1.snap