Link: https://lemmy.world/c/bern@feddit.ch

A few months ago, I joined the lemmy platform and made my account here on lemmy.world.
One of the first things I searched for was a community of my hometown, Bern.
I was happy to find one and subscribed successfully (seemingly) : https://lemmy.world/c/bern@feddit.ch

Soon I noticed that not much is going on there and I tried to activate life there by making a few posts. I got a few votes, but no comments.
This didn't trouble me too much; I just thought that there were just very few users in this community and that those were very passive. I kept on making posts of which I hoped that they could be motivating people to get into active communication, or to subscribe, if some non-member found this community.

Today I tried to subscribe to this community from piefed.social. I wanted to demonstrate a friend the interoperability of the two services lemmy and piefed. I couldn't find the Bern community, though.

Then I realized that the whole instance of the Bern community (feddit.ch) had been shut over 2 years ago!
I tried to dig deeper into this, and finally found this post announcing the shutdown of the instance : https://lemmy.world/post/12995344https://lemmy.world/post/12995344

So my question is: is this community still alive and real? Or is it some zombie copy that I posted into, but it doesn't really live or it's not really visible or accessible to users on other instances, or maybe even on this instance?
If so, shouldn't it be eliminated somehow?

Since the instance itself is dead, federation won't work.
Basically the way it works now is it needs to be removed from each individual instance.
An admin could also decide to lock it instead of deleting it but there's like 3 posts in it.

It seems to me that this situation - an instance shutting down and community copies continuing to exist on other instances - has a potential frequency of a few times per year or more.

So, I wonder if there is no standard process, best practice, checklist, or any other recommendation by the development team of Lemmy?

Concretely:

if any stakeholder (user,...) discovers a zombie group copy, what shall he do?

Is there no measure to prevent the situation that users join zombie group copies again and again? Like the one I joined; it is still there. Each day other users could find it, be happy to join it and be frustrated by the resulting experiences.