For upcoming travel to Austria, please note that COVID restrictions have been further relaxed on April 16. Notably, FFP2 masks are now only required in essential shops, in taxis and on public transportation. The 3G proof rule (tested, recovered, vaccinated) has also been lifted for all areas, including Vienna.
Here is the link - https://www.austria.info/en/service-and-facts/coronavirus-information
As an anecdote, I flew yesterday from Amsterdam to Vienna. The Austrian military was randomly checking COVID documentation from arriving passengers. I only saw one person stopped from our flight. It would probably be a difference if arriving from outside the Schengen zone.