How to synchronize Fossify Contacts contacts?

[cdauth]

After years of working with raw phone numbers, I have finally spent a bit of time researching how to manage contacts properly on Android without the risk of giving malicious apps access to my whole contact list. I have found the Fossify Contacts app. It seems to manage contacts in a separate database in its own app storage, so other apps don’t have access to it, except the Fossify Phone and Fossify Messages apps so that the name of the recipient is shown when making calls/texts.

Now I thought that since I have DAVx5 already set up to synchronize my calendar with Nextcloud, it would be nice to synchronize my contacts as well so that I have a backup and can also access them from my computer when needed. However, I must say that I don’t really understand how this works and haven’t been able to find much information about it. As far as I understand, DAVx5 synchronizes Android’s central contact storage, not the internal storage of Fossify Contacts. The only thing that I could find at all is a feature request for Fossify Contacts to synchronize using CardDAV directly, but it was denied.

Is there a way to synchronize the internal Fossify Contacts contacts? If not, what setup are people using to synchronize their contacts? Is everyone using huge phones where they can install a custom operating system that allows configuring for each contact which apps can see it? Or are people keeping sensitive contacts that should not be seen by malicious apps somehow separate and do without synchronizing them?

[ArnyminerZ]

Hi, Fossify Contacts uses the same system database as all the other contacts app, which is the same that DAVx⁵ synchronizes into.

You can see all the accounts by clicking the filter icon in the top right corner; it will display all the contacts accounts in the system.

If you believe this is not the case, please, contact again with details.

Is everyone using huge phones where they can install a custom operating system that allows configuring for each contact which apps can see it?

I don't know about other ROMs, but GrapheneOS (which is probably the largest security-focused ROM out there) can either give access to all contacts, or "simulate" access; which makes the app believe it has access, when it doesn't.

Or are people keeping sensitive contacts that should not be seen by malicious apps somehow separate and do without synchronizing them?

I guess, again, either do not grant access, or keep your sensitive contacts out of the device.