A QR code is required by local authorities? That seams like quite a strange requirement. The invoice is available and printable that should cover every country. At any rate no I don't have a solution for you. There are no plans to add QR code invoices, sorry. Are you sure this is necessary? That seams like a requirement for brick and mortar stores not online subscriptions.

We've no solution for generating QR Codes or means of meeting these requirements, sorry. Suggest contacting a lawyer or financial adviser to see if you really are subject to needing QR Codes. Based off what I'm reading it seams aimed at brick and mortar stores, but they don't really clarify.

Have added a feature ticket that will implement a trigger before invoice is displayed so you can use a custom integration, or CB Auto Actions, to completely replace the invoice rendering with a custom output. Will try to have this available sometime this week so you'll be able to have it output whatever you like.

forge.joomlapolis.com/issues/9134

A new CBSubs build release is now available with this trigger implemented. Usage example as follows in CB Auto Actions.

Global
Triggers: onCPayAfterDrawInvoice
Type: Code
User: Automatic
Access: Everybody
Action
Method: HTML
Code:Output
Display: Silent
Layout:Method: PHP
Parameters
References: Variable 2

You'll now notice when viewing an invoice it will just say "Hello!". You can use this functionality to completely replace the invoice rendering with your own behavior as needed. You can access the invoice object using var4 which gives you access to the cbpaidPaymentBasket object and all its data in the _cbsubs_payment_baskets database table (e.g. [var4_mc_gross] or can be accessed from PHP rendering with $variables).

If you need further explanation of variables and what information they hold for your usage don't hesitate to ask. This should let you completely replace invoice display with whatever requirements you may have. You will need to implement your own QR Code generating behavior.