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
the former’s honestly a godsend in setting up alt accounts
ya fr i used it to copy settings to shitjustworks and lemmee, i don’t think my instance is going anywhere any time soon but ya can never be too careful