Just finished testing and this one is working!
You can consider this one solved.
However, if you need some more information on this, let me know.
Thank you for the support.
I have synced DAVdroid on my Android mobile with CalDAV on my Synology NAS, works great.
Having some difficulty with CardDav however.
If I go into my DAVDroid account which I setup for my calendar I see two sections, one for CalDAV where I have my calendars setup, then one for CardDAV. If I attempt to add a new addressbook under CardDAV the “home set” field is already prepopulated with the url for my calendar and I cannot edit it.
So I setup up a separate account for an address book, select “Login with URL and user name”. Enter url as per https://www.davdroid.com/tested-with/synology/ and username and password and create account.
Oddly the new account has a calendar entry (and includes the calendars I have setup for my other account), nothing for contacts.
What am I doing wrong?
This helped me resolve:
Was not using the correct port