Not sure, but I don't think so. I think it's only if that site itself can link the IP to a name / user. For example, storing all the real world addresses in the world doesn't require a GDPR notice, but they're all related to people.

IP addresses match the definition in GDPR article 4 point 1: they are "an identification number, location data, an online identifier". Well the second one has to be stretched a bit, so an address matches location data, but the other two fit quite well.

If those are the only criteria, then I think it doesn't fit.

When I still live in the UK 6 years ago, IP addresses were rarely fixed, and changed everytime you connected. In fact, people paid extra to get a fixed IP.

I guess it's a bit of a grey area though, since sometimes it fits, sometimes it doesn't.

no those are not the only criteria, see gdpr.eu/article-4-definitions