How do you sync your contacts? I’d like to get rid of the iCloud and my Apple ID entirely, but I need it so far to sync contact data in between my MacBook and (currently still) iPhone.
I use my personal NextCloud instance to sync contacts and calendar between my MacBook and iPhone. Also, for that matter, I use my NextCloud instance to sync my KeePass file (Keepassium has the ability to sync via WebDAV).
You will need your Apple account in order to access the Store.
And, I found the hard way, if you setup a new iPhone from an encrypted local backup it won’t restore the actual applications: It remembers which ones you had but it will need to download them from Apple. So you can’t run any downloaded app until you have logged into Apple.
I had a situation where I had a long impossible (at least for me) to type password for my Apple account and I needed that to setup the store so I could download an app to access my Keepass file to get the password. PITA.
Edit: P.S. I found the easiest way to setup CardDAV and CalDAV accounts on the iPhone was to have a mobileconfig file setup. You can get the Apple Configurator app on the Mac store and use it to create a file that sets up access to arbitrary CardDAV and CalDAV servers. I also use it to setup access to my mail accounts and home WiFi network. Then all I need to do is AirDrop that file to my phone and all those are setup correctly with no extra typing, etc.
The answer is CardDAV.
I use the encrypted CardDAV and CalDAV from Posteo. You can use the system Contacts app itself and works well. If you save a new contact on iOS, it gets saved in your new address book on Posteo but is still accessible on your Apple devices as normal.