HTML5 email field non-latin characters

Originally email addresses could only use the characters a-z, 0-9, and a few symbols, but in recent years this has changed. The HTML5 input type "email" rejects addresses where the local part contains diacritics. For example, the following is rejected:

Élève@somedomain.com

The PHP7 FILTER_VALIDATE_EMAIL is also rejecting them

It probably is not a good idea to use diacritics in email addresses, but that isn't the issue today. I have people in France trying to add email addresses containing diacritics and my validations are rejecting them. It isn't appropriate for me to preach to these people about the wisdom of their email address choice.

I could find a regex to solve this, but I am disappointed and surprised that HTML5 and FILTER_VALIDATE reject these characters.