Not right now. Murat from the Ghost team confirmed earlier this year that Ghost’s ActivityPub server has no domain migration yet, so the new domain gets a fresh account with zero followers: What happens to my activitypub account if I change domain?
Best you can do: keep the old site running until you’ve posted a note from the old handle with your new handle in it, and give followers a few days to follow you there. Only then switch the old domain to a redirect. Once it redirects, the old account stops working and you can’t reach those followers anymore.