I have tested the email trigger with SharePoint Designer 2013, the same result as yours.
I found some other users said that the same issue existed when December 1st. Similar question: https://powerusers.microsoft.com/t5/General-Power-Automate/Emails-are-coming-from-SharePoint-Online-no-reply/td-p/2500605
It may be caused by SharePoint development team changes the From address setting. From users' perspective, we cannot change the From address setting.
I suggest you open a service request with Microsoft to get more detailed information.
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