Can an account be deleted from the client side?

I am making a system where the users can play as guest via a device id base Nakama account, and when they sign up for an email account, I want to delete the device id account to avoid cluttering the database with inactive accounts. Can this be done from the client side? If not, how can I do it from the server side?

I think the best approach would be to link that email+password to the same guest account and then unlink the device id from that account(only if you want to keep that device id free for guest account).
Check this out for more info - https://heroiclabs.com/docs/authentication/#link-or-unlink

Yes. It’s as @hdjay0129 has recommended. You don’t want to create accounts from different social providers or linked identities. Instead you want to create the account through some initial mechanism and then link other providers to that account so it can be reached (“authenticated”) with via any of the authentication options supported by the server and configured for that user account.