You need to make sure that you activate the P2 trial by using an Entra ID user account, not your Microsoft account. This would allow you to activate the P2 trial within your existing Entra tenant. If you don't have an Entra ID user account, simply create one, ensure that it has the Global Administrator role, sign in to the Entra Admin Center (or Azure portal) by using this account, and activate the trial.
Note that this still requires that you provide your credit card information, however, you will not be charged for the trial
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hth
Marcin