Hey,
If you're trying to buy your GVB subscription from GVB web or app, you'll come across an IDEAL list that doesn't have bunq included.
The thing is, it's not possible to move on due to bunq does not have a physical identifier, as ABN Amro does. In oder to solve it, you can buy your subscription directly from GVB Tickets and Service in any metro station and the costumer service will be able to add it to your subscription.
It would be nice if they fix it, until it's done, here it goes an alternative solution.