I have a voucher, but Kayo wants me to provide a credit card

A valid credit card is a requirement for a Kayo subscription, even if the monthly charges are covered by a voucher. This ensures that when the voucher expires, the Kayo service continues.

https://help.kayosports.com.au/s/article/12-months-of-Kayo-Basic-with-AFL-Digital-Membership#offer-ends