Okay, I have Ubuntu 16.04 and installed oC by sudo apt-get install owncloud-client and had some 2.1 version installed.
Now I tried to follow the instructions but have some authentication issues when updating.
I used sudo apt-get purge owncloud-client to remove it.
then I added the Repo to my apt-list.
I tried to update but had some broken dependencies. I used sudo apt autoremove and sudo apt-get install -f
After that I was able to update again.
Now I am back at the start:
and still cant fix it.