Why has one of my boards changed owner to someone I don't recognize??

@james brooks -  I am going to suggest that this type of question would be best handled by Miro support as the community members would not have the resources to do the type of investigation required in order to determine what has happened. Therefore, as per this post: Do I Need to Contact the Support Team or Ask the Community? :

If you are looking for official, in-depth support (regarding billing issues, technical questions, etc.), or you have run into an issue (lost content, features not working, other bugs), please reach out to the Miro Customer Support team directly by creating a ticket via this special form.

I would just that you open a support ticket with Miro right away.

@james brooks - You’re welcome! I hope the support team can sort this out for you quickly. It would also be helpful for the rest of the community if you were to come back here and share what the Support team told you.

I understand your frustration around finding a way to contact support. Even for the paid users who are listed as the only plan type with support available to them (see the bottom of this page), the link is quite buried:

That being said, the link is accessible to all Miro users and I have yet to see them not help a Free/Education Plan user.