I think Scandinavian peasants were alone in Europe to never have been serfs. Which probably has cultural effects even today.

One explanation I've seen is that if the nobility got to aggressive, Swedish peasants could always go hide in the forest for a while.

...which is something you can do in a low population density land, and we're full circle :)

The Black Death also helped a lot. It reset a lot of property relationships by leaving a lot of free land after farmers and their whole families died out - in Norway it took about 200 years before most of the farms were back in operation, and when the population was expanding again there were tax breaks for restarting farms. We can see the extent of it today in the prevalence of last names like Ødegård, Ødegaard and similar (literally "deserted farm"), and similar place names.

Danish peasants were serfs for a period:

https://en.wikipedia.org/wiki/Stavnsb%C3%A5nd https://en.wikipedia.org/wiki/Vornedskab

Sounds more like what China is doing, you need a pass to move to the city.

Forests in Europe are not exactly unique to Scandinavia.

Thing is much of the peninsula due to the climate can support only marginal agriculture and hence only a very limited peasant population. Not enough pop density to establish any sustainable lifestyle for nobility.