I use NextCloud (fork of OwnCloud) to manage my contacts[1]. It has a CardDAV interface. Synchronises contacts with my phone, and live lookup for my email clien

I use NextCloud (fork of OwnCloud) to manage my contacts[1]. It has a CardDAV interface. Synchronises contacts with my phone, and live lookup for my email client too. Very nice having a single-source-of-truth contact list. [1] In fact, that's all I use it for. Don't use any of NextCloud's other functionality.