My eldest is a a freight pilot and flies all over Europe. He also sees different regulations all over the place.
At some airports, he lands, freight is unloaded and loaded and he flies off to the next destination. Turnround time of an hour or less. They don't leave the plane except for the pre flight walk round they have to perform at every take off, even if he has landed the same plane just 30 minutes earlier. There are airports where he has no Covid checks. There are others where they have their temperature taken. If it's over the "border" temperature for that country (some as low as 38, others up to 0.8 higher) he would have to quarantine for however many days that country specifies, anything between 7 and 14.
At others they have layovers of anything between 8 hours and 3 days. Wherever he is, one thing stays the same. A taxi picks them up at the plane, takes them to the hotel. At the end of the layover a taxi picks them up and takes them directly to the plane, airside. Where it differs is what happens at the hotel.
At some, they check in, go to their room and have to stay there till it's time to fly. Some of those hotels have security staff on each floor to make sure you don't leave the room. At others, they have the freedom of the hotel but can't leave the hotel. At others they are free to tour the city. At one layover, a lad we know, also born in our village, lives there. My lad can't visit his mate at his home but his mate can visit him at the hotel.....
A hotch potch of different rules wherever he goes.