The usual rule of markets applies: anything any person can do to earn money is already being done at scale. The idea of earning in a high-wage locality and living in a low-expense locality certainly isn't new.
Freelance work can have good hourly rates, but that usually comes with insecurity.
I know people who charge 250€ per hour, but the number of billable hours on average per month is rather on the low end because their customers basically expect them to turn up, solve the problem and leave as quickly as possible, and the timer stops when they go to the bathroom.
There is a happy medium where people charge 50–90€ per hour, and effectively work the same as regular employees, but with no benefits or protections. These jobs tend to be on-site, and while the yearly income is high, the lack of predictability has a lot of drawbacks, for example a lot of rental contracts stipulate a minimum rental period that is longer than a typical project contract.
On the lower end, there are some contractor positions for simple tasks, like adjusting color schemas in websites or writing GUI dialogs. These don't pay well, generally, but there is a steady supply of these contracts, which gives a bit of security. Usually these have a coordination requirement like going to a weekly meeting in-house, and the rest is work-from-home because the customer does not want to invest in office space and equipment for one-off projects like rebranding an application.
The automated freelancer brokers are not seen as serious work, these are mostly used by students wishing to cheat on their exams, and by companies who need a quick mock-up for a demonstration. There seem to be very talented people on these sites with impressive portfolios — projects I'd bill a month for are listed as "done in three days for $500" — but whether they actually exist is questionable.
Last but not least the true digital nomads — most of those that I know are well-established freelancers who have specialized in a field where customers generally need their services only for very short amounts of time, and where enough customers exist. A lot of these jobs seem to be performance tuning, like routing policies for overseas network cables, or storage management for large datasets — basically things you do not want to change during normal operation, so a full-time support person makes no sense.
As with any market, these are mostly optimization problems being solved at scale by having lots of people with different strategies filling different niches. If there was an optimum strategy, everyone would be doing that. Instead, people place themselves on various axes like "desire to travel", "desire to know how much money I will have next month", "desire to see friends" and so on and then see what is possible within those parameters.
One person I know who is happy with "digital nomad" style basically knows people in every city, so wherever the current job is, they call someone and meet for dinner. Expensive, yes, but they have basically been able to work around any political crisis in the last ten years by simply going somewhere else — but that is a different kind of "security" than having a house and a family.
