there's a whole two hundred post debate around here whether ip are or aren't pii on their own, with the wast majority holding the wrong position.
there's a whole branch of gdpr that people aren't considering, which is not related to software but to your business (i.e. your mail calendar). you also need a privacy policy if you are receiving phone calls. did you know that?
there's a whole bunch of implication on how liable you are about holding unwanted personal information, including unwanted medical personal information i.e. "hi I saw your gazebo renting service, I'm organizing an event but I am unable to walk due a permanent disability and requiring a ramp is present to access your gazebo, is that so?"
there is a huge surface area for uncertainty, up and including 'best practices' that are a constantly shifting target.
edit: to clarify the calendar part: if you have a meeting with someone, that links an identity with a location. that's why it's an issue, even without considering the address book, which is another issue by itself.
THe problem is that it's a stupid question. No-one has just IP addresses, they have a mix of data. If you can combine the IP address with anything else to identify a natural person it becomes personal data.
It’d be really nice for the “fucking idiots” that you referred to earlier if those of you who clearly know what the law says and what it means could get your stories straight.