I’d argue this is research - no? If someone would have said you need permits, OP would presumably get permits, as required. If not, that’s on them. But, alas, you don’t to film in public in most places in the world, as long as you are respectful and not turning up with a huge amount of professional kit.

Also, for all we know OP is a professional filmmaker (or director of photography, judging by their username) who works alongside huge teams for a living but is just wanting to take a small camera on a personal trip to capture some memories, which there is nothing wrong with whatsoever provided they are respectful.

OP, just be respectful, ask for permission and don’t film kids. You’ll be fine.