Complement severity forms: How to disable WP's default emails, but allow serious emails to pass?

I have a problem with our new WP site
We use gravityforms for user registration and everything works as expected
The user verification email is sent and, after activation, the user receives the welcome email, both correctly configured in severity.
But, in addition, the new user receives generic emails from WP with plain text at the same time, so it is not very professional to send 2 emails to a new user.
I tried several add-ons to prevent WP from sending those "default" emails, but I could not find any solution
Does anyone here have an idea to solve this?

Thanks in advance