With the vlemmy situation ongoing, i feel like it would be useful to put this here (i did not make either of these tools)
Lemmy Account Settings Instance Migrator (LASIM) copies all your subscribed communities and blocks and lets you upload them to another account, in just a few clicks
lemmy-migrate does the same thing but without a GUI and support for uploading your backup to multiple accounts at once
Hopefully in future this is built in to the software. Ideally you’d be able to download a JSON/XML file from your settings page for your settings/subscribed communities then upload them to a different instance similar to how it works with Piped instances, for example.
mastodon also has this feature built in and i would love to see it come to lemmy
It’s currently being worked on as a native function of Lemmy
https://github.com/LemmyNet/lemmy/pull/3480