YMMV depending on your org, but with the right environment (aka, Okta org features), you CAN create/have users that have a unique login/username, but all share the same primary email. This is what I have done with test users in my own org so that I can get the activation and email MFA emails sent to my own email, while still creating those users with their own unique usernames (with bogus email addresses, etc).
Can you check if you are able to do this in your org (not all orgs can)?
Yes, I can check. If it doesn’t offer me the option to create associate multiple logins with one email then I just assume that I don’t have the feature? Is there a way to verify the feature is available?
You can reach out to support so they can check what you have enabled. For example, I believe this will not work in a free Developer org because the Self-Service Registration feature was enabled in those orgs by default, and it enforces username and primary email to match for user creation.