Automatically backup contacts to local file

Hi there.
I've been using Davx5 to sync my contacts to an online WebDAV server. This doesn't feel optimal to me.

I'd like to find an an Open Source app (or at least a Freeware app) that will backup my contacts to a folder of choice on the phone's local storage (interna/external doesn't matter).
I would then proceed to sync that file with Syncthing to other devices that I own.

Does anyone know an app that will do just that? TIA
Cheers