Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
I get - too bad
Sorry, this offer is for new customers only.
Of course that is wrong.
It's a general feature available to any and all Office 365 personal or Office 365 home users.
In the beginning it was in beta and limited to a limited sub-group of users, but looking at the FAQ this restriction is not mentioned any more, so it is probably productively available for everyone now.
Follow the FAQ and you will find it. I have a european contract myself and it worked nicely since last fall.