Comment 7 for bug 1991813

Looking further, the documentation at https://ubuntu.com/server/docs/install/autoinstall-reference#apt is not explicit. One must follow the link to https://curtin.readthedocs.io/en/latest/topics/apt_source.html where the configuration of a PGP key is documented.

It is then possible to install 22.04 with an internal repo managed by Aptly. The only caveat is that the parameter "Acquire::AllowReleaseInfoChange "true";" must be defined because Aptly rewrite the Release files when publishing a repo, which indeed crash the installer. To my understanding this is related to Aptly, not to Ubuntu.

I have been able to complete an unattened install through PXE with the user-data file below:
```
#cloud-config
autoinstall:
  apt:
    primary:
      - arches: [default]
        uri: "http://mirror.acme.tld/mirror/ubuntu/"
    conf: |
      Acquire::AllowReleaseInfoChange "true";
    sources:
      aptlyrepokey:
        key: | # fill key as block
          -----BEGIN PGP PUBLIC KEY BLOCK-----

          [...redacted for readability...]
          -----END PGP PUBLIC KEY BLOCK-----
  identity:
    hostname: dummy02
    password: $1$QuiloverocknrollTs5nMdFgH/
    username: ubuntu
  [... some other parameters not relevant here...]
  version: 1
```