A quick clarification about the instances list I posted yesterday: it is not a list of dead instances, my bad. As @loke pointed out, https://mastodon.sdf.org/ is alive and well.

The process I started on monday was checking all remote accounts of this instance (about 115k). These accounts are followed by or follow one or more accounts of #functionalcafe.

The remote account can be unreachable for different reasons: the instance is down, the ssl certificate of the instance is no longer valid or the remote user doesn't exist anymore.

At the end the process (tootclt accounts cull[1]) spits out a list of all the instances involved.

[1] https://docs.joinmastodon.org/admin/tootctl/#accounts