Value for "Display name publicly as" during registration

[Santy4tas]

Hello dear community,

I have a problem during registration. I've forced the registration forum to use the user email as the "Username" value, that's how I need it work for my website, so far so good, the problem comes with the following.

I need to assign a different value to the Display Name Field because the Actions Pack Elementor Form is putting the user email in the Display Name Field, of course this is a problem caused by me because I'm forcing the email to be the username, but it's not necessary to have the username in the Display Name Field as a must. Maybe you can wonder "Why I need to change this?", this is because having an email in the Display Name Field is consider an error for some user profile edition in Woocommerce.

I have tested a lot of things:
The first one is let Actions Pack Form auto generate an username taking as reference another field, for example, if I use the email field as the reference and the email is SandraWCox@mail.com the most probably thing is the auto generated username would be something like SandraW or something similar, this could fix my problem taking into account the following reasons:

The new registered user will have the auto generated username value in the following fields:
Username (Obviously)
Nickname
Display name publicly as

This is not a good solution for me because I need to force the username to be the email, not a random auto generated username.

Although the user is registered like this, the Nickname and the Display Name can be changed in the Wordpress edit user options, without the need to coincide one with the other, neither with the Username.

The above let me think in the possibility to assign the first name as the display name since the registration, automatically.

I've tried "Additional Fields" option in the Actions Pack Elementor Form but I couldn't been able to find a "Display Name" meta. I tried too to use the "Custom Meta" option using a meta key like "display_name" without success.

Someone have an idea what I can do?

How can I register an user putting the Email in the Username field BUT putting the First Name in the Display Name?