Old man here. Never had a credit card. Don't believe in them. Kids have had Spriggy debit visa cards for years and use them to buy Steam games (under some supervision) so it would be working as intended on that side. Doom Eternal, bought with a non-bank adult debit visa is still showing in the family library.

Edit: Ok, confirmed this shit show does appear to be real. We can run purchased games from the family library but can't view them in the store and a minor bank adult debit visa doesn't unlock age verification. Another angry parent letter to the office of Anika Wells I guess. Can't entirely blame Valve when the legislation is half arsed and broken.

Edit 2: As inconvenient as it is choosing only CC verification it might be reasonable choice for Valve. I don't want to use some dodgy third party verification service and its probably a good thing that isn't being presented as an option. Most of the blame has to be with the eSafety commissioner, Communications minister and everyone who voted for the legislation.