Apt sources missing in autoinstall environment (22.04.2)

I am setting up a network autoinstall with the 22.04.2 image. With a packages key, the package installation step fails. (I thought it was working last week.) When I look into the target environment, all apt sources except cdrom are missing:

ubuntu-server@ca2-t-it02:~$ ls -la /target/etc/apt/sources.list.d/
total 8
drwxr-xr-x 2 root root 4096 Apr  8  2022 .
drwxr-xr-x 8 root root 4096 Apr  5 21:48 ..
ubuntu-server@ca2-t-it02:~$ cat /target/etc/apt/sources.list
deb [check-date=no] file:///cdrom jammy main restricted

If I remove the packages key and interrupt the install by forcing an error in late-commands, sources.list looks correct at that point. So it looks like I can get around this by doing the installs in late-commands, but it would be much nicer if it worked as advertised (https://ubuntu.com/server/docs/install/autoinstall-reference#packages).

Here's my autoinstall file:

#cloud-config
autoinstall:
  version: 1
  apt:
    geoip: false
    preserve_sources_list: false
    primary:
      - arches: ["default"]
        uri: http://us.archive.ubuntu.com/ubuntu/
  timezone: UTC
  identity:
    hostname: newhost.example.com
    realname: Local Administrator
    username: myadmin
    password: "<redacted>"
  keyboard: {layout: us, toggle: null, variant: ''}
  locale: en_US.UTF-8
  network:
    version: 2
    ethernets:
      srvnet:
        match:
          macaddress: '00:50:56:b3:bc:c9'
        set-name: mynet
        dhcp4: false
        dhcp6: false
        addresses: [ 10.1.1.213/24 ]
        gateway4: 10.1.1.1
        nameservers:
          search: [ example.com ]
          addresses: ["10.1.100.10", "10.2.100.10"]
  ssh:
    allow-pw: true
    authorized-keys: []
    install-server: true
  packages:
  - sssd-ad
  - sssd-tools
  - realmd
  updates: all
  storage:
    layout:
      name: lvm