I have an iPad (not iPhone or Mac). If you don't set up Icloud, there's always an annoying bright red circle in settings that tells you to "finish setting up your iPad".

Doesn't have to be bright red, or even there at all.

Last time I had that on a laptop I was going to wipe soon afterward and didn’t want to fully set up, I clicked the “finish setting up” link and canceled out. Voila, red circle gone.

Gone until a few days or a week later, when it comes back.

Yes, that’s the only one I’ve seen. But it’s not much of a nag.

There's several of them. The most annoying for me was getting intermittent notifications to sign in to iCloud.

There's also this one: https://discussions.apple.com/thread/250727947

I eventually just gave in to stop the nags.