Please see https://forums.bitfire.at/topic/1674/what-is-the-2-letters-after-the-account-name-for-address-books and the links there (especially the manual)
I am trying to use the select and “share” feature in contacts on my stock Samsung S5 via the share icon.
Contacts that exist in the main book share fine using the different methods (BT, wifi direct, es save to, email, …).
Contacts that are created by Davdroid refuse to generate a vcf to share. In K9 email it simply opens without any attachment, for some other methods it flashes a message about not generating the data.
I am using Davdroid 188.8.131.52-ose, android 5.5.1 as my sender. I have tries multiple recipient devices including a samsung core, S7, and Huawei GR5. They all work as expected when the contact to send is in the device phonebook.
Sounds like a problem of the branded Contacts app. Unfortunately, many Contacts apps assume that there can be only local and Google contacts
If you really need this, you could try another Contacts app or a custom ROM like Linage.