I have to provide a polish phone number.
To register it is enough to provide an email. That`s what I see in FAQs.
But
You need to provide your phone number later on while arranging the settings of your account.
This is how it looks like during registration.
Sorry, I don`t open links from unknown people.
This way or another, it seems nobody here can help you.
Why don`t you send your enquiry to Allegro directly????