I’m using an OPPO A16 smartphone (Android 11) on which I installed apps from F-droid and among these, the applications “Messagerie SMS” and “Contacts”.
I added numbers and names of my contacts through one and the other of theses apps but after an our or so, when I look for them (to make a call or to write a message), I can’t find them anymore, they have disappeared from my contact list. And the line above the SMS conversations indicates only the phone number (no name).
For your information, I previously deactivated as much apps of goggle as possible on my phone in order to use as much of their F-droid apps equivalent as possible.
I already saw this.
In my phone, since the beginning, i have deactivate most of google parts, no problem. I have do the same with my sister’s phone, but having a google count probably created by the salesman, there is an app (i don’t remember the name) witch synchronize contact data with google. By disabling it, she have lost all of her contacts.