Turn off syncronisation of contacts in LineageOS / CyanogenMod
In the syncronisation screen you have to turn Synchronisation on global. Only if that is on you have checkboxes next to each category inside the google account. you can uncheck the box at Contacts then.

If the global sync is OFF you don't have this option.

I think it is a bit dangerous the first time you enter that menu, because you have to be sure your internet connection is disconnected. Otherwise the first time, when all sync boxes are still ON it will start right away to sync everything before you have the chance to disable the sync-box for contacts.

If you are offline you can setup everything like you wish and then it's fine.