Supporting 'vanity' URLs for KnowBe4

We'd like to be able to create a URL that is 'friendly' or familiar to our users (like 'cybertraining.company.com') which would just be a DNS CNAME that redirects to our KB4 login domain (like eu.knowbe4.com). This would help staff be confident with a familiar service (ie our domain) and encourage them to safely navigate to the Department's supported awareness platform (KB4).

However this doesn't work - We receive a CLoudFront 403 Gateway error when our DNS CNAME points to KB4.

Alternatively having support for '(companyname).knowbe4.com' would also be of some value.