I'm fine with restrictions if they are reasonable/justified. I don't have an app store and I'm not planning to use one, and it's unclear to me why I'm unable to download and print a ticket when they can do the same for €50.

From a personal computer there are zero requirements, I don't need to have a special OS, or application, or anything. On the mobile application side, I must have one of two authorized app stores, an account there, and perhaps a specific OS version. This is something that I find unfair in this business practice.