After reading the guidelines you provided, I do not think Manager is required to generate QR codes. The rules seem similar to our country.
The invoice details are sent to your govt portal where an e-invoice is generated with a unique hash. This hash is included in the QR code generated by the portal and this is what you need to print on the invoice.
So Manager needs to facilitate sending the required invoice details to such portal and download the generated QR code which should then be displayed on the invoice.