I'm afraid it only works for that one instance:

I am subscribed to:

but not to:

So I have to chase the ones and resubscribe manually.

That's ok if I know about it, I can just search for all lemm.ee ones I'm subscribed to, go there and find the post which tells me where the community is moving. But sometimes it takes time for the community to decide and I probably will miss it like https://lemmy.sdf.org/post/35941084

Anyway, just so that everybody is aware of that fact and doesn't miss resubscribing to the new ones.