Yes possibly...
But it is only what YOU will do with the data that bothers.
No data is mandatory, so you may not store these data if you don't need them.
Moreover, these data are "professional" one, not "personal" (you may not store personal phone numbers

)
I know RGPD is very ambiguous about this and does not clearly distinguish "personal" from "professional" data but clearly explains that RGPD does not concern data only used in the execution of standard work for professional use.
I don't think storing profesionnal email to send work information to user enters RGPD scope.
Otherwise, I guess Outlook should include RGPD processus... (yes your web client stores emails or your contacts)
Anyway, I've added a ticket to include RGPD information process in ProjeQtOr.
I think what is important is to be able to display a message at least once and keep trace that user really has read the message
As of today, an information message on the login page is the best you can do.