If so perhaps you could ask for a copy of your data that lemmy world has on your former accounts, and report to the regulator if they ignore your request. Not sure if federation helps or hurts - like could you say that lemmy world must have something of your data since other federated servers still have a copy of your content?
Would be nice if there was a way to use the GDPR here to bring some addtional accountability to the lemmy world admins.