They added it in Chef 15 (https://docs.chef.io/resource_snap_package.html), but I can't find a cookbook for it on Supermarket, it looks like they implemented it straight into Chef
I have added the kosmos.chat domain to the Let's Encrypt cert, so there should not be anything to do for TLS for the migration:
I was able to try this in a VM and found a way to migrate the room data (options and affiliations) to the new host:
It was merged to master but not the stable-2.9 branch. Currently it's 382 commits behind master: https://github.com/tootsuite/mastodon/tree/stable-2.9/app
I ran into an issue generating the Elasticsearch indices, but I found a PR that was merged into master that's not part of Mastodon 2.9.3 that fixes it: https://github.com/tootsuite/mastodon/pull/11192.
The node name is set automatically from the server's hostname so that is not needed. The default cluster name is elasticsearch, do you have a suggestion for a name?