How can we encourage the older generation to actually use QR code payments (or digital payments, for that matter)?

More than often, it is the resistence to change and the lack of functionality of their existing mobile phones. It is not uncommon to see seniors holding phone merely for phone call and not using any of the apps. It might be too challenging for them. Personally I feel, they have to first get comfortable with their phone and be open-minded to try. Once they are comfortable, you may start teaching them how to navigate and use the apps. Then slowly venture into transaction-based action such as using QR code. Basically, taking steps to build up their confidence and mobile literacy.

Take time to explain to them that this is going to be the future. Probably need to demonstrate a few times for them to see and let them do hands-on. After a while, they will actually find it convenient.