I liked your list and wanted to add my own. I'm not really into Apple products; I use an iPhone because my wife threatened me with physical harm if I didn't.

Generally, I use Linux, so I want to use things on my phone that I can also access from my computer.

- Mail -> Fastmail

- Calendar -> Fastmail

- Maps -> I do use Apple Maps. It is not great, but it generally gets me where I want to go. I refuse to use Google for anything.

- Reminders -> (Reminders app has one job, which it doesn't consistently do...) Fastmail snoozed and scheduled emails

- Music -> The Pirate Bay + foobar2000

- Drive -> Syncthing

- Books -> The Pirate Bay + Onyx (Reader)

- Weather -> Local News Site