Danish immigration laws are also very strict. Most of our political parties have been competed to further tighten those rules over the last couple of decades. We literally have people advocating to leave the convention on human rights, since it’s getting in the way of that

Visa-wise, they are probably just committing fraud by staying on a tourist visa.

French immigration is currently allowing remote workers on the one year visitor visa, so long as your company doesn't have a presence in France. Basically, as long as you are not doing business in France or taking a job from a local they are fine with it.

However, it's difficult to proceed to a residency permit in this situation, and you can't join the national healthcare system.

VPN. Simple as that. Most companies aren't bothering to check anyway, most that do aren't detecting VPNs, and for the few that do that, there are ways to circumvent detection if you are really determined.