I think the assumption that infected people have extended immunity is generally considered to be a workable one, though not a proven one as yet - but as I recall the virus has mutated remarkably little since it started, which would tend to imply that immunity would be stable too. But yes, herd immunity probably does mean most people getting the disease at some point. The trouble is, given we can't maintain a lockdown to a timescale big enough to allow for a vaccine to be produces, most people will get the disease. The best we can do is try to keep its progress below the capacity of the intensive care system until we have a vaccine - what other plan is there? Letting it run riot means unacceptable loss of life, but we can't eradicate it realistically either by any means other than herd immunity or vaccinations - no lockdown, no testing regime, will be quite thorough enough for a disease this widespread. And we can't maintain total lockdown for a year and a bit without mass casualties from lots of other problems.
I think we actually do have a decent handle on how many people are dying in Austria - that's rather clearer, if not entirely so, than trying to work out infection rates.
The masks for shoppers thing seems to be having an awkward roll-out - which is to say, I went shopping today and did not wear a mask at any point, because, well, there weren't any being given out at the shop, or indeed any on sale at the shop, and I can't create them by magic. I guess maybe the bigger supermarkets are rolling them out first? Meanwhile I still don't have hot water, my arms are to put it gently buggered, the humidity in my flat is a mess and teaching is exhausting. I've been listening to Wolf 359 a lot and finding all the stuff about being on a space station with repeatedly failing life support systems really quite relatable to my situation. Except I'm lacking the wisecracking AI voiceover to talk to.