How to create a Custom Payment Method with QR (Bakong KHQR) in POS (Odoo 19)

Hello community,

I am working on Odoo v19 POS and trying to integrate Bakong KHQR (Cambodian payment system) as a payment method.

So far, I have:

• Created a custom module with a pos.payment.method extension (new fields like token, account, merchant info).
• Added form view fields for the payment method.
• Added assets (payment_bakong.js) for POS.

The problem:

• I can save payment methods in backend.
• But I cannot display the KHQR code on the POS payment screen.
• My current XML view inheritance fails with xpath (error: Element '<xpath expr="//sheet/notebook">' cannot be located in parent view).

Questions:

1. What is the correct way to extend the POS payment screen in Odoo 19 to display a QR code (dynamic/static)?
2. Do I need to use OWL (Odoo Web Library) components for the POS frontend or can I rely on pure JS/QWeb templates?
3. Any working examples/tutorials for extending pos.payment.method with custom fields visible in the POS UI?

Resources:
pypi.org/project/bakong-khqr/

Thanks a lot for your support 🙏