This isn't America. AK won't help you sue based on suspicions of discriminations if you don't bring written evidence that makes it a slam dunk case. And the court isn't biased towards the employee like the US jury.

exactly, this isn't america. despite not needing to have a specific reason for letting someone go you are not allowed to use morally questionable reasons (which goes beyond outright discrimination), and you must evaluate how the loss of employment affects the employee. that means, for example, the likelihood of that employee finding a new job with similar pay, (so you can't easily let go of older people), their family situation, or if they have another income. so you basically have to choose the employee who would be least affected. as far as i understand these kinds questions are not considered at all in the US. only discrimination againt protected classes, as defined by the law.

Austrian law isn't US law, correct. I still don't understand your persistent pessimism though...

What I once saw when I went to the Arbeits- und Sozialgericht was a man, in the beginning of his 40s, suing for unlawful termination of his employment contract, after notice period and 7 months of employment. He sued with the help of the Arbeiterkammer. The judge asked the employer for their reasons, and tried to figure out if the termination has been made through thoughtful reasoning and after consideration of any other options. It is the responsibility of the employer too(!), and frankly in their best interest, to bring their employees up to speed and make them succeed in their work.

"We don't need to state any reason" won't fly in front of the judge in Austria, as the judge wants to make an informed decision.