Thanks for the response, @devvv4ever ! You raise some good points about duplicate contacts and merging algorithms, and I agree that such ideas are well beyond the scope of DAVx5. However, I have yet to find a FOSS (or even just freely-available) app that does a good job of simply copying contacts between accounts. Samsung may have one, but I don’t have a Samsung phone.
My plan for merging the CopyContacts app I linked into DAVx5 was to create a new DAVx5 contact store for any existing contact store the user wants DAVx5 to manage. Basically, like you, I also wanted to avoid the issue of contact merging. Sure, this would create a lot of extra accounts/contact stores, but it would at least allow existing contacts to be merged (and synced) by DAVx5.