People in Montenegro: it's not .yu, it's .me
EDIT: apparently, "asking DNS servers for all the domains they know about" is not something you can really do anymore for security reasons. Guess that idea won't fly lol
On the other hand .su (soviet union) is still in use.
It is very unfortunate ICANN still hasn't address this issue yet. Although not yet, .io is in a similar situation with even larger domains active but the territory is changing hands from britain to mauritius.
World is connected by Internet, it needs to be preserved even after geo politics and borders change.
Neighbors, brothers, friends, who spoke the same language and occupied the same cultural space, suddenly reduced to their narcissism of small differences and committing horrible atrocities in the name of a tribe.
And for what? For the chance of living in a dysfunctional rump state with nowhere near the relevance of what they used to have.
If Yugoslavia got a political transition as it happened in Spain to a social-democracy, (and yet the Spanish constitution states that all goods belong to the state in case of general intereset, such as a great catastrophe), they would evolve together and wars would have been a thing of the past.
As an anecdote, read about the creation of the Warajevo ZX emulator, a cross-ethnic colaboration from several Yugo people to get spare PC parts and books while avoiding snipers.
BTW: a country not existing is not an excuse. The Catalan language stretch over Spain, Andorra (the official language) and a bit of France and Italy. Ditto with the Basque language (and .eus domain).
.Yu could be reused for content written in Serbo-Croatian language. Ah, yes, the Cyrillic script, but today that task would be trivial, and I'm pretty sure that due to the exposure to the Latin scripts the Serbians can read Croatian texts perfectly fine.