Almost 15 years ago (omg!), I crossed the Sarek National Park together with some friends in summer. It indeed deserves the title of “Europe’s last wilderness”.
The hike was great since we had quite stable weather – it can get “interesting” in case it rains a lot since this could make you stuck between smaller rivers coming down from the surrounding mountains. Rivers can grow quickly up there.
In total, if I remember correctly, the trip took us around 10 days – afterwards, we spent some additional days on the Kungsleden in order to get back to civilization. However, the Kungsleden is a highway compared to the Sarek through-hike.
Our starting point was Ritsem which can be reached by car / public transport. From there, we took a short ferry trip to get over the Akkajaure. From there we hiked multiple days down to Aktse where we got on the Kungsleden again. Quite a good report can be found here.
A few years ago I thought about returning to the Sarek in summer with the packraft – however, new regulation does not allow this anymore. DZJOW has a nice report about his packrafting experience in the Sarek.
It’s somehow a pity but also an understandable argument in order to protect the environment. In the end, it always depends on how you, the visitor, treat nature – obviously there must have been some issues with this challenge so that authorities had to enforce this new regulation.