Hello Valentin
In Odoo 17, Odoo deprecated the triggers On Creation, On Update, On Creation & Update, they were replaced by the trigger On save.
This trigger is called whenever the record is saved whether its creation or updating the record, however you can utilize the When updating Field to perform the action only at creation.
For example you can set the field When updating to Created On or Created By, As these fields only change at the creation of the record.
Here is an Example of how your rule will look like

I hope this helps
If it helps please upvote my answer and Mark it as Correct