https://docs.joinmastodon.org/admin/tootctl/#accounts

> `tootctl accounts merge`
>
> Merge two remote accounts into one. This is primarily meant to fix duplicates caused by other servers changing their domain. By default, this only works if the public key is the same, but this can be overridden.
>
> Version history:
> 3.3.0 - added

これってつまり、Mastodonのデータベースやpublic/systemの中身と.env.productionとredisをごっそり持っていけば別ドメインに移行できなくもないってことか。