Largely pointless. EU courts have in the past ruled that IPs are personal data because they can be tracked back to a person. End of story.
>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).
was largely already covered by the previous EU privacy law and the german privacy law. Courts largely agree that calendars for appointments are fine as long as you keep them reasonably secure and don't throw them around in public.
>you also need a privacy policy if you are receiving phone calls. did you know that?
Yes I did. I informed myself when I registered as a small business.