Many articles were published the last weeks that Covid crises lead to a hype (which was already existing before) of outdoor activities, camping, etc. Especially in national parks it is causing problems: less silence for the animals and quite often waste is left behind. Nonetheless I tried to organize a hiking/tenting trip in the Austrian Alps and comply with all laws. It was not easy and in the end it was half tent, half huts but I will try to share my research. Please keep in mind that laws can change, sometimes they are vague and that hunters, hut owners,... also have interests in the mountains and are financially depending on guests.
And please keep in mind that the conditions change depending on season, how hard the winter was and that some things I have not done myself but just give ideas and cannot tell if it works well like that (especially camp grounds where we didnt stay and path conditions which vary every year, this description is from end of June 2020)!
Begin of planning
The laws differ quite a lot between the different European countries (in Scandinavia it´s very liberal, in Central Europe rather restricted), even within Austria there are huge differences. To summarize them: camping lower than the tree level is always forbidden, emgerency (!) biwak is always allowed. In some federal states it is less restricted: Upper Austria (Oberösterreich, OÖ), Styria, Salzburg and Voralberg. In the others it is very strict, Voralberg I did not do much research because it is a bit further away.
So to concentrate on the first 3 states: if you are above tree level it might be fine. But first restrictions are national parks where it is never fine: in OÖ there are Nationalpark Kalkalpen (which has two legal biwak places), in Styria Gesäuse and in Salzburg Nationalpark Hohe Tauern. So if you go there use the marked places and the huts! Then there are different other kinds of nature protection: sometimes with restrictions, sometimes it is more for advertisting but without further laws.
In Salzburg most interesting areas are Landschaftsschutzgebiet or nationalpark, here you can check it yourself: just tick the right boxes and you will see how little will remain.
In Upper Austria Totes Gebirge is an option but not too much water there so it is difficult with lakes, rivers. There is a reason why the mountain range is called like that. Upper Austrian Dachstein area should work though, Styrian part of Dachstein and Totes Gebirge (Wildensee) are under protection. On Dachstein one hut is even offering it to sleep at their area (Gjaidalm). The 30 euros include breakfast, dinner and of course you can use all the infrastructure at the hut! For a first attempt it is a great idea! Access either lazy with cable car or hiking up to train your back for future adventures already!
In Styria the Schladminger Tauern are under no special law. There is just the area of the Klafferkessel (clearly stating that camping is forbidden there, this shows the protected area), where you are not allowed to tent, so either changing to huts or making a long day trip to avoid staying somewhere over there.
Our decision was to go from Obertauern to St. Nikolai im Sölktal as it seemed to have the best premises for tenting as much as possible without getting in conflict with anyone.
This was the route we planned to take, stopping mainly around lakes sounded good to have flat ground and water. Took be extensive research to create it, in the end it is more or less the same what the Schladminger Höhenweg follows so could have had it all easier. So let´s start with the trip itself and how it all worked or did not work and why.
Access public transportation
Depending exactly how you want to do your trip there are different options, starting in Obertauern and descending somewhere for Schladming or going to Sölktal (altough from there public transportation is worse). We started from Obertauern Passhöhe and got picked up from Sölktal, one option would be going from Preintalerhütte via the Höhenweg Planai to the cable cars of Schladming and from there to the train station.
Access car
Parking in for example Schladming and maybe taking a bus to have a different start from end point.
Hiking
Day 1: We went by train and bus via Salzburg to Obertauern Passhöhe and started there towards Obersee. Due to a sign lying on the ground and bad orientation it all lead to a 2 hours detour and the orginal aim to reach the Giglachseen to camp there was getting out of sight. In addition it was raining like hell and the ground was terribly wet. When reaching the Obersee there were also several signs which forbid camping so the decision was taken to avoid wet ground and sleep in the Oberseehütte. Home-made milk, very good food and a warm place made it the right decision and so we could continue the next morning without having all stuff wet and starting straight away with a wet tent which might have stayed like that with the upcoming forecast.
Day 2: Via the Akarscharte (2315m) we went to the Giglachseen. If you have time and motivation from the saddle there are two peaks to go to (Kalkspitzen) and then you can descend to the two lakes. Beautiful views on the way down and from the Akarscharte there might be views to glaciers, but with our weather I have no idea if this is correct. Around the lake there are two huts and some more cabins but it seemed possible to camp there. Bit higher is the Brettersee located, without infrastructure so I suppose camping there would be fine.
From the Giglachseen there is either the option via the Rotmandlspitze (2453m) or via the Duisitzkarsee. We avoided the peak due do the uncertainty of snow fields and chose the easier but timewise longer path around the mountains. The Duisitzkarsee is not suitable for camping, below tree level and several cabins around so we proceeded towards the Keinprechthütte. Some time before reaching it we found a clearing close to Neualmen with cow shit but without cows and decided to spend our first tent night there, bit off the road and not too visible. That is also something to keep in mind: staying away from animals, taking their sleep and also the danger that they run over the tent or join you for dinner or breakfast. For dinner/breakfast/warm night the Keinprechthütte is perfectly located!
Day 3: Towards the Reinprechthütte but not reaching it and turning to the left to cross another mountain range. Via the Trockenbrotscharte (2237m) the path goes then down to the Landawirrseen. On the lower one there is a hut, on the higher one it seemed decent for tenting. If you do not need to descend like us you can continue on a Höhenweg towards the Gollingscharte and skip ascending and descending for like 300 metres and just enjoy the views from the top. The crossing till the saddle was one of the areas with the most snow, in early season it might be also closed, there are signs indicating this in case!
Till the saddle with needed to walk around 200 metres all the way up through snow. Existing steps and warm weather is helping! In case temperatures over night are cold and you go in the morning, crampons might be recommended to avoid slipping, in general with steeper snowfields take poles or axis to keep balance, long clothes in case of slipping that no skin injuries occur and just start slowly and not with the biggest and steepest snowfields to get used to the different conditions. From the saddle the option Hochgolling is waiting. Detour will be more than 3h and it´s a hike including climbing of difficulty I. As our backpacks were heavy and walking through snow is not always funny we just proceeded and got to an amazing valley with many many young (and older) horses.
The hut is advertising this circular deep vally as the biggest nature amphitheatre of the world. Just the Hochgolling northface is already very impressive and can compete with other big alpine faces!
Down in the more flat area it was difficult finding a camping spot, partly very wet and many horses which we did not want to disturb and interfere with them. We continued towards the Gollinghütte and when I was "afraid" that we will sleep over in the hut, we found a decent spot next to the river, not very wet, flat without much cow shit. Turned out perfect as moist in the ground stayed okay and tent didnt got wet at all. Finally our rations of food got less and we could cook a bit and enjoy the view. After dinner there was still a lot of time to kill so we visited the horses another time.
The Gollinghütte: beautifully located!
Day 4: The next day lead us through the glacial lakes in the Klafferkessel, kind of the kings´s stage (Königsetappe) on the whole track and if you want to camp something to certainly plan well, last option before getting into the protected area is the Sattelsee on 2450m. As it is rather high keep snow, cold temperatures and wind in mind. All the lakes on the Styrian side (including Sonntagskarseen) are protected, as well as the ones on the Salzburger side (Zwerfenbergsee,...) so the next options are rather far away and start after the Trattenscharte, maybe with the Goldlacken. But better than making an extensive stage anyways would be staying at the Preintalerhütte. One of the nicest hut keeper (Hüttenwirt) I have met so far! Great food cooked from his wife, as a dessert Pofesen are highly recommended. To quote the Hüttenwirt: "hot, fatty, sweet, what else do you want", we can confirm. 
In the back the impressive south face of Dachstein.
The big glacier in the back is from Ankogel, dark mountain face to the left is the Golling and the snowfield on the saddle to the right of it is the Gollingscharte, where we were coming from.
View from Greifenberg into the Klafferkessel.
In the right back is the Greifenberg, the mountain we were starting with before getting into the Klafferkessel. Many lakes were still covered in snow, nearly 30 mountain lakes are located here.
Day 5: Quite many people will end there trip here and leave via the vally or a ridge (to the Planai and then down to Schladming by cable car) back home but we planned to continue a bit more and had the options either via Trattenscharte or Rettingscharte to the Sölktal/Schwarzensee. Forecast was bad so we got advice from the Hüttenwirt and he said that with rain and in general via the Trattenscharte it is better because the descent is not as annoying. Rettingscharte via Sonntagskarseen has the advantage that you see more lakes but on the other hand they are quite similar to the ones from the day before.
The area around the saddle had enormous snow fields and it sometimes felt like walking on a glacier, but rather flat so was relaxed to walk and no need to be afraid. Going down to the Goldlacken and the Grimming became visible the first time. Till now Dachstein was often visible just on the opposite site of the Ennstal.
Descending got with more rain worse, GPS tracks on watch definitly helped as due to snow some parts of the path were still covered and an alternative needed to be walked. On the way we also met a German couple, they wanted to go the opposite way, we gave them some advice but in the evening met them again, the man left a helicopter and we hoped that nothing too bad happened. Luckily his wife only broke her ankle but the whole rescue was quite fortunate: for them the rain turned into hail and they turned around again, wife slipped and could not continue. Weather cold and wet, cloud foggy so it was quite lucky that the helicopter could find a window to rescue them, otherwise it would have taken hours till the rescuers would have gone up, even connection to call for help is not always secured. So when packing keep such possible emergencies in mind to pack enough warm clothes, food, drinks, headlamps, rescue blankets to survice some time till a possible rescue. Broken ankle, especially with moist ground, can happen quite fast, experience, poles and higher shoes are helping but there is never a guarantee.
Another tip: if you have a camera not being waterproof, insane rain is not the time to use it, also not when standing in a cave because fingers, hood, sleeves are all wet and some cameras are not too keen on such conditions.
At the saddle Karlkirchen there is also a big cave, which should be suitable for a biwak or as well just for a rest with bad weather (or shade with good weather). Our tour then ended at the Breitlahnhütte.