The context for this error is the May 2021 policy "How to prevent crypto mining abuse on GitLab.com SaaS", which then triggers:

This thread illustrates there is no easy solution.
Issue 331959 follows the problem and:
We are considering multiple things:
Better ways to validate users that are not going to do abuse that doesn't create steps for legitimate users that are of no value to them or get in their way of using the product (AKA credit/debit card validation).
The timeline is a couple of months out and it may not be fully successful depending on how the abusers adapt to the controls in place and try to subvert them.
Potentially allowing SMS validation in addition to credit/debit card validation for users.
I believe it is also likely a couple of months out.
I am personally working on advocating for making it so that if an account is on a free plan but buys pipeline minutes, that the users for that namespace do not need to validate their account before running CI jobs.
The work to enable this is not huge but is also not trivial, and there are concerns about it potentially being used by abusers to avoid our other controls to start a new avenue of abuse.
So for now, individual verification remains needed.
Verification through svipe.com
might be an alternative which would not require to enter credit card.