Not always of whole populations (though often that too) but individuals travelled much more freely.

At least part of the reason that individuals traveled freely is that only rich individuals traveled.

Paupers from London didn't get on ships to the new world - not without selling themselves into indentured servitude.

When the economic barriers to migration fell to the point that subsistence farmers could travel between continents, we were always going to see either an equalization of living standards or the rise of political barriers.

Yes.

Even before the adoption of visas, the traveling experience for a first class passenger on a ship was very different from third class getting routed via Ellis Island in the US.

Not in the majority of Europe, especially places like England or Poland which had strict restrictions on what serfs could do for hundreds of years.

Part of the reason for Britains diverse regional dialects is due to this.

That was within the country though, right? Not between countries? And this article [1] says enforcement of serfdom was localized and costly and there was de facto serf mobility.

[1] https://broadstreet.blog/2021/05/07/serfdom-the-state-and-th...

I don't know about peaceful but you could move. There were no visas and in fact no passports. Though, trying to get inside a "city" (ie: citadel) might be tricky. I guess they used gifts before to convince the other party.

That being said, if you settled somewhere in some large empty land, no one will complain.

> That being said, if you settled somewhere in some large empty land, no one will complain.

That's because any empty land would probably be entirely unsuitable for a settlement.

Obviously we haven't specified a period in history but this all sounds suspiciously rose-tinted to me.

Plenty of land was suitable for settlement (ie: Argentina). Mostly empty and competing empires were too far. Of course, after the discovery of the "new" world, the amount of empty land reduced significantly.