Adding existing iPhones to DEP/Intune

IPhone: 5s, IOS 11.x.x

Apple Configurator : 2.5 (3F60)

IMac 27" Mid 2010 MacOS Sierra (10.12.6)

Here is our situation.

We recently enrolled in the DEP to facilitate the process of delivering iPhones to our users. As we are bound
by a contract with our phone provider, it was not possible to have them pre-enrolled in the program so we have to do it manually, which is now possible with IOS 11.

So I created a blueprint in Apple Configurator to add the devices already purchased, in the DEP. Our phones are new, have never been unpacked and have never been supervised.

My first issue is that in the official documentation of the Apple Configurator, to configure a blueprint for preparation for DEP, I would be supposed to have a window that proposes the option not to register the device to an MDM.

As I am forced to do so, I added the unique URL of my MDM created from another mechanism for adding
iPhones to Intune, Apple Configurator.

My second issue: In addition, by creating a DEP preparation blueprint, I am force to supervise my device from the Apple Configurator on my Imac, something I do not want because when I created a DEP enrollment profile in Intune, I had the option to supervise the mobiles. As a result, once the preparation for the DEP is
complete, I have to add an extra task to erase the settings and content on each of the phones to remove its supervision.

I found out that if i didn't wipe the phone after applying the DEP Schema, when the end user was receiving their phone, it didn't show the screens that i specified in the Intune DEP Profile. It was the profile created in Apple Configurator that showed up...

So here's my unofficial procedure to add our iPhones to the DEP/Intune:

1- Update our devices to the latest IOS

2- Apply a Wifi profile (because our phone don't have any cellular plan yet and need to contact the DEP from what i understand)

3- Apply the "Add to DEP" blueprint

4- Clear content and settings (to remove the apple configurator supervision)

5- Re-application of the Wifi profile

Then in the portal deploy.apple.com, I download the list of serial numbers in the server "Mobiles added by Apple Configurator". I copy these serial numbers and add them to our "Intune" server, which has been previously configured in the portal.

Then I head into Intune to start a synchronization with the DEP and then assign a management profile to our newly add iPhones.

Once an Intune license is assigned to a user, I can distribute the phones to the end user and the steps
defined in the profile created under "Enrollment Program Profiles" work.

Am i doing Something wrong ?

Does anybody in here that are in the same situation as us ?

Can anybody explain to me what i am force to define an MDM server in the preparation action ?

Is it normal that i have to wipe the phone again to remove the supervision from Apple Configurator ?

Any help would be really appreciated.

Thanks a lot