Is Microsoft Entra ID P1 required to use SaaS Alerts?

Microsoft Entra ID P1 Licensing for your customer is recommended but it's not required to use SaaS Alerts. Microsoft provides additional information via APIs for tenant Organizations that have a Microsoft Entra ID P1, and SaaS Alerts has developed some features to take advantage of that information. SaaS Alerts was specifically developed with the Business Basic / Free Azure Ad tenant in mind. 

A P1 license is required to allow for data gathering for our MFA report and to view SSPR information as well.

Be aware that while one P1 per tenant may work, Microsoft's policy is that every user must have a P1.  

List of the licenses that include a P1:

AAD_PREMIUM
AAD_PREMIUM_AAD_PREMIUM
AAD_PREMIUM_MFA_PREMIUM
AAD_PREMIUM_P2
AAD_PREMIUM_P2_AAD_PREMIUM
AAD_PREMIUM_P2_AAD_PREMIUM_P2
AAD_PREMIUM_P2_ADALLOM_S_DISCOVERY
AAD_PREMIUM_P2_MFA_PREMIUM
EMS_AAD_PREMIUM
EMSPREMIUM_AAD_PREMIUM
EMSPREMIUM_AAD_PREMIUM_P2
EMSPREMIUM_ATAENTERPRISEPACK  -  Office 365 E3
M365_F1_AAD_PREMIUM M365 F1
SPE_F1_AAD_PREMIUM
SPB - Microsoft 365 Business Premium 
SPE_E3 -  Microsoft 365 E3
SPE_E5