Gregory's Server
I have a friend that died in June 2022, months after setting his instance over Musk in April 2022. He is the only admin for the instance of 14 users and it is still going. I'm not sure how it is still going. Luckily, it is on Masto Host and they do upgrades & it is set to auto approve new registrations, already. Maybe some linked payment account the family doesn't know about and when it dries up the domain will go stale.
@paul Hopefully the users on that instance have already migrated or otherwise abandoned. That thing could go at any time.