@Nico Tedeschi - There are two ways to move a board from one Free Plan team to another:

1. Use the Move to team action.
2. Open the board, click on the board name, and use the Duplicate action.

For number one, as long as the Miro account profile, i.e., email address, is a member of the team where you would like to move the board to, then you can right-click on the board in the dashboard (or use the ellipsis), and select the Move to team action - just pick the team where you would like to move the board.

For the second (Duplicate) option, all you need to do is to

1. open the board’s Share settings,
2. set the “Anyone with the link” to “can view”
3. open that board as the user where you would like to move the board to,
4. click on the board name
5. use the Duplicate option.

The second option may be easier.