Comment 3 for bug 2031409

My guess is that there is confusion around a given track and architecture and a charm that claims multiple architecture / multiple base support.

Specifically, if you download ubuntu_r24, then it has this in metadata.yaml:

series:
  - focal
  - bionic
  - jammy

and this in manifest.yaml:
bases:
- architectures:
  - amd64
  - arm
  - arm64
  - i386
  - ppc64
  channel: '18.04'
  name: ubuntu
- architectures:
  - amd64
  - arm
  - arm64
  - i386
  - ppc64
  channel: '20.04'
  name: ubuntu
- architectures:
  - amd64
  - arm
  - arm64
  - i386
  - ppc64
  channel: '22.04'
  name: ubuntu

Which does indicate that it supports all the architectures for 22.04 with that version.

That said, I'm guessing that at some point in the past revision 21 of the charm was uploaded to just the sub channel latest/edge amd64, probably with metadata that didn't indicate it supported "all" versions.

That does, generally, indicate that there is inconsistent information in charmhub itself:
$ juju info --base ubuntu@22.04 ubuntu
name: ubuntu
publisher: charmers
summary: A pristine Ubuntu Server
description: |
  This simply deploys the Ubuntu Cloud/Server image
store-url: https://charmhub.io/ubuntu
charm-id: DksXQKAQTZfsUmBAGanZAhpoS4dpmXel
supports: ubuntu@18.04, ubuntu@20.04, ubuntu@22.04
subordinate: false
channels: |
  latest/stable: 24 2023-05-26 (24) 2MB amd64, arm, arm64, i386, ppc64
                     21 2022-09-15 (21) 2MB amd64
  latest/candidate: 24 2023-05-19 (24) 2MB amd64, arm, arm64, i386, ppc64
                     21 2022-09-15 (21) 2MB amd64
  latest/beta: 24 2023-05-19 (24) 2MB amd64, arm, arm64, i386, ppc64
                     21 2022-09-15 (21) 2MB amd64
  latest/edge: 24 2023-05-19 (24) 2MB amd64, arm, arm64, i386, ppc64
                     21 2022-09-15 (21) 2MB amd64