What are some public places where It is ok to loiter?

Parks are for loitering.
Probably not at a police parking lot.

The local gaol.

An indoor Mall, okay.

A Loiter Box. That’s where my cats loiter.

Note – this is both an answer to best and worst place to loiter.

I loiter at the public library, makes me look smart. hehe

Loitering in a dark alleyway at night would be a very bad place to be.

You can loiter on a beach for a long time. Also at a bus stop.

I would avoid loitering on certain street corners.

It would not be a good idea to loiter in front of a mail-in ballot collection box

Public docks. Avoid playgrounds.

Good- Farmers market

Bad- Grade school playground

Back in the stone age when phones were actually phones and you had to buy a dedicated GPS if you wanted positional information, I was in Washington, DC for a meeting. While there, I decided to find a geocache that someone had hidden just outside the fence near the White House. Yes. That White House! I was being very discreet and only peeking at my GPS occasionally while walking slowly to get bearings. Any time someone approached i put everything in my pocket so I would not be noticed. Very discreet indeed.
At one point, I pulled out the GPS for a peek and while distracted, someone snuck up behind me unnoticed. Some big guy murmured into my ear: “I know what you’re doing. Just keep going. You’re heading in the right direction.”
I quietly said “Thank you.” and found it.
So bad place to loiter? In front of the White house.

Above Russian positions in Ukraine, if you are a loiter munition.