I can't make it work on my Windows 10 VM. I even removed all email accounts to try it from scratch. I first added my @outlook.com account, which is associated to a Microsoft 365 Family account, but the option to set this account as the primary account is grayed out.

Assuming that this means my @outlook.com is by default the primary account, I tried to add any of my other accounts, for which I have an Exchange Online Plan 1 subscription, but I receive this message:

PS: I am currently upgrading my licenses to Microsoft Business Basic, because from what I can tell it will not work with Exchange Online (Plan 1). I will update this post when I know more. The license cost for me increases with 51% as the Exchange Online (Plan 1) costs me 4,44 EUR/license whilst Microsoft Busienss Basic is 6,72 EUR/license.