Hi, Alex, I would suggest reading this article on how to bulk edit the post authors so that way you can easily and quickly change the author to be the one that you want: https://kinsta.com/knowledgebase/how-to-change-author-in-wordpress/#bulk-change-authors
I would then delete the user that you don’t want to keep anymore.
Thank you very much! It ended up a bit more complicated than that because of the Jetpack thing, but disabling Jetpack and then re-setting it up again under the correct login did the trick before I moved the posts and deleted the account I didn’t want.
