Mobian Update/Upgrade Troubles

[Joseph Ciurej <joe@churay.xyz>]

Greetings Mobian team,

I recently tried updating my repos for the first time in a few months
and I ran into some difficulties. In particular, running `sudo apt
update` caused the following errors:

E: The repository 'http://repo.mobian-project.org mobian Release' no
longer has a release file.
N: Updating from such a repository can't be done securely, and is
therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user
configuration details.

Poking around on the Mobian website, I saw mention of the imminent
expiration of the Mobian PGP key (source:
https://blog.mobian.org/posts/2022/06/30/tmim/#pgp-key-expiry) and
followed the instructions to download the latest version. After fumbling
around with `apt-key` for a bit, I executed the following commands
(the command on the website was invalid; it seems like it's missing an
`apt-key` command, e.g. add or update):

```
# apt-key add mobian.gpg
# touch /etc/apt/trusted.gpg.d/mobian.gpg
# apt-key add --keyring=/etc/apt/trusted.gpg.d/mobian.gpg mobian.gpg
```

Unfortunately, further attempts to run `sudo apt update` resulted in the
same errors and now I'm stumped. Do you have any guidance for how I can
fix my key store and start receiving updates again? If it helps, I'm
running factory settings on a PinePhone Community Edition from early
last year (see: https://www.pine64.org/2021/01/17/mobian-community-edition/).

Thanks in advance for any help that you can provide!

Best,
Joe