Unable to deploy charmed-kubernetes on Big Sur macos

I can confirm that I get the same error on an older version of OSX. It looks like the 2.8.7 client is missing a piece :-/

Reproducible with:

$ juju deploy cs:~containers/kubernetes-master-926
ERROR kubernetes-master is not available on the following series: focal not supported

However, kubernetes-master does support focal in the metadata.yaml.

The problem really does appear to be client side. I did the following:

1) Bootstrapped a controller on aws with juju 2.8.7 on macOS High Sierra:

    juju bootstrap aws aws-osx-test

2) Attempted to deploy the ubuntu charm with series focal:

    juju deploy ubuntu --series focal

This failed with the error documented above.

3) Grant an "ubuntu" user privileges to access the default model on my new controller:

    juju add-user ubuntu
    juju grant ubuntu admin default

4) Deploy from an ubuntu machine running the 2.8.7 client:

    juju register ... # output from add-user above
    juju switch admin/default
    juju deploy ubuntu --series focal

That last step worked! I'm also able to add units via juju add-unit from the Mac. Not sure where the check is in the client, but it does look like a client side check that is failing.

After some discussion ...

At present, this is actually working as designed. Juju 2.8.x doesn't officially support focal. Juju 2.9.x is the series that was intended to release alongside, and support, Ubuntu focal.

Unfortunately, several things have happened:

1) We've delayed 2.9.x.
2) The 2.8.7 client takes a look at the supported distros file on Ubuntu systems, and works with focal, despite not officially supporting it.

I think that we need a better long term solution for how this works. For now, you can deploy to focal from a MacOS box with the --force flag. For example:

```
juju deploy ubuntu --series focal --force
```

(I'm going to triage this bug to the backlog for now, as it will be fixed for the next year and a half by the release of 2.9.x, and we can revisit when the next LTS comes around.)

This Medium-priority bug has not been updated in 60 days, so we're marking it Low importance. If you believe this is incorrect, please update the importance.