@Kevin Tahon Thank you for reaching out to us, As I understand you want to enable push notifications for adb2c mfa, verified this requirement with my internally on this, currently push notifications for Azure AD B2C is not supported.
Verified methods which are available are documented here - https://learn.microsoft.com/en-us/azure/active-directory-b2c/multi-factor-authentication?pivots=b2c-user-flow#verification-methods ( same as per your screenshot ).
Let me know if you have any further questions, feel free to post back.
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