You could create a QR code that takes you to the Feedback activity and then display this QR code where needed.
If it's meant to be feedback for the system as whole, you could create a course that uses the single activity format and select the feedback activity (opens in new window).
The general workflow for the user would be:
Scan QR code
User is prompted to log into Totara (by whichever method you have configured)
Upon successful login, the user is taken to the enrol page for the feedback activity
The user selects enrol
The user can now complete the feedback activity
There are different ways to create a QR code for the activity.
Chrome (opens in new window) and Edge (opens in new window) browsers (and there may be others) allow you to share pages via QR Code.
Hope this helps and provides you with a starting point.
Georgina