We have updated our FAQ page about contact groups because it seems that Android 8 has re-invented contact groups.
In the screenshots, you can see how contact groups look on
- Google Contacts (default app) from Android 8 (SDK emulator)
- LineageOS 14.1 (Android 7.1.1) on a Samsung Galaxy S2
- Android 4.4 on a Samsung Galaxy Note 10.1
- "real" contact groups (introduced in VCard 4, but back-ported to VCard3 with vendor-specific properties), where the group is stored in a separate VCard and contains a list of all its members, and
CATEGORIES(available in VCard 3, the minimum VCard version that has to be supported by a CardDAV server), where each contact is tagged with "categories", which then form the contact groups.
It's important to choose the correct method (the one which is used by your server) when adding the DAVdroid account (see the Configuration pages; or you have to find out the method from the server manual or by trial).
Almost all group operations are supported in both modes:
At the end, it should be mentioned that Android (AOSP) has a bug that prevents contact group creation in the Contacts app for third-party contact providers like DAVdroid. We have created an AOSP bug report plus patch which allows creating groups for DAVdroid accounts. Unfortunately, our patch hasn't even been looked at since Aug 6, 2014.
LineageOS and OmniROM have integrated the patch to improve group support for external sync adapters like DAVdroid. With LineageOS 14.1, all group operations work well.