Glory holes are definitely a thing. I know of a current one in a toilet at a nearby park. I say "current" because authorities generally shut them down. This one had a huge slab of sheet metal put over the entire partition between cubicles, and someone with the right tools for the job drilled out a perfect circular hole again, lol.
There are glory holes in some adult stores that have cinemas and dark rooms. A local club in my area installed them after covid restrictions eased, presumably as a way of maintaining social distancing, and I even heard of a Canadian health authority encouraging use of glory holes to limit covid transmission. One way to find local glory holes in your area is the website "Squirt dot org" which lists local "cruising" locations. You get a short period of membership for free when you can use it to search.
I sucked one dick at a glory hole but I'd pre-arranged it with the guy on a hook-up site. That was in a derelict public toilet (which has since been demolished, owing to its sordid reputation) near a sports ground. He messaged me that he'd arrived, I walked from my car to the toilet, and entered the cubicle which had a circular hole drilled at cock height in the door. I closed and locked the door, sat down and waited. I heard him come in, and I signaled with my fingers in a "come-on" motion through the hole, withdrew, and waiting a moment. Soon, a hard, thick shaft came through the hole. It seemed weird to see it and not see the guy; I'd seen and sucked plenty of cocks, but to see one just emerge through a hole, like it was disembodied, seemed both strange and exciting. It also kind of keeps on emerging and you don't know how long it will be until he's pressing against the door or partition. I guess it was about 6.5", thick and smooth, cut and very attractive. I licked, then pursed my lips on the tip and slid him deep into my mouth, and went to work. Soon he was thrusting against the door and it was making a banging sound against the latch. I thought FFS, everyone around the park will hear us. Very soon he stopped thrusting, I heard a soft moan, and a stranger's disembodied cock erupted into my throat. I gulped down every spurt and kept him in until he was done, then he went slightly soft and the cock slid back and away from the hole.
He messaged me afterward on the app "10 out of 10, thanks mate" (Australian men call each other "mate").
I never did it again at a hole and I haven't been game to staff the current one at the park. I'm not typically into glory holes, I'd rather see the guy and have some connection with him, and gauge him up, even if it's a random stranger. Also the risks don't appeal to me in a public toilet. People who go there to take a piss might not take kindly to it - can I defend myself against violence? Yeah but I'm not invincible. That one I've seen the police visiting. You should consider the consequences if you get arrested. It's much safer from that point of view to find a glory hole at a sex venue.